Adds new scroll driven Animation properties - #32

Leave the four scroll-animation properties to microsoft#32 and accept digit-prefixed @Property names consistently with the valid custom-property syntax documented in microsoft#43.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Bound the scope leak from unclosed `@container` and `@scope` preludes
with `(?=\{[^)]*$)`. Recover at `{` only when no `)` follows on the
same line, preserving legal balanced blocks in declaration values.
Do not use `;` as a bail-out: `<general-enclosed>` permits top-level
semicolons through `<any-value>`, and legal preludes may span lines.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard every parenthesised region reachable
inside a prelude with `(?=\{[^)]*$)`: recover at `{` only when no `)`
follows on the same line, preserving legal balanced blocks in
declaration values. Guarding only the outermost regions is not enough,
because an outer `end` cannot be evaluated while an inner rule is
active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude with `(?=\{[^)]*$)`: recover at `{` only when no `)`
follows on the same line, preserving legal balanced blocks in
declaration values. Guarding only the outermost regions is not enough,
because an outer `end` cannot be evaluated while an inner rule is
active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` unguarded. A `var()` fallback may legally contain a
balanced curly block spanning lines, and guarding it truncated that
value; main does not recover an unclosed `var(` either, so the
exception gives up nothing main provided.

Give the `:lang()` and `:dir()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude with `(?=\{[^)]*$)`: recover at `{` only when no `)`
follows on the same line, preserving legal balanced blocks in
declaration values. Guarding only the outermost regions is not enough,
because an outer `end` cannot be evaluated while an inner rule is
active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` unguarded. A `var()` fallback may legally contain a
balanced curly block spanning lines, and guarding it truncated that
value; main does not recover an unclosed `var(` either, so the
exception gives up nothing main provided.

Give the `:lang()` and `:dir()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude with `(?=\{[^)]*$)`: recover at `{` only when no `)`
follows on the same line, preserving legal balanced blocks in
declaration values. Guarding only the outermost regions is not enough,
because an outer `end` cannot be evaluated while an inner rule is
active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` unguarded. A `var()` fallback may legally contain a
balanced curly block spanning lines, and guarding it truncated that
value; main does not recover an unclosed `var(` either, so the
exception gives up nothing main provided.

Give the `:lang()` and `:dir()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude so they recover at `{` only when the rest of the line
does not close the parenthesis, preserving legal balanced blocks in
declaration values. The test is lexical rather than a plain `[^)]*`,
because a `)` inside a comment, string or escape does not close
anything: without that, `@container (width > 1px{ /* ) */` stayed open
where main recovered. Guarding only the outermost regions is not
enough, because an outer `end` cannot be evaluated while an inner rule
is active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` and custom function calls unguarded. Both are
declaration values, and `<declaration-value>` admits a balanced curly
block that legally spans lines, as in `--x: --foo({ ... });`. The legal
`--foo({` and the malformed `--foo(a{` are indistinguishable within a
single line, so recovering there would cost legal CSS that main scopes
correctly. Main does not recover an unclosed `var(` either.

Give the `:lang()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude so they recover at `{` only when the rest of the line
does not close the parenthesis, preserving legal balanced blocks in
declaration values. The test is lexical rather than a plain `[^)]*`,
because a `)` inside a comment, string or escape does not close
anything: without that, `@container (width > 1px{ /* ) */` stayed open
where main recovered. Guarding only the outermost regions is not
enough, because an outer `end` cannot be evaluated while an inner rule
is active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` and custom function calls unguarded. Both are
declaration values, and `<declaration-value>` admits a balanced curly
block that legally spans lines, as in `--x: --foo({ ... });`. The legal
`--foo({` and the malformed `--foo(a{` are indistinguishable within a
single line, so recovering there would cost legal CSS that main scopes
correctly. Main does not recover an unclosed `var(` either.

Give the `:lang()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container`
coverage for the gap first identified in microsoft#15, and accept digit-prefixed
`@property` names consistently with microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude so they recover at `{` only when the rest of the line
does not close the parenthesis, preserving legal balanced blocks in
declaration values. The test is lexical rather than a plain `[^)]*`,
because a `)` inside a comment, string or escape does not close
anything: without that, `@container (width > 1px{ /* ) */` stayed open
where main recovered. Guarding only the outermost regions is not
enough, because an outer `end` cannot be evaluated while an inner rule
is active. Do not use `;` as a bail-out: `<general-enclosed>` permits
top-level semicolons through `<any-value>`, and legal preludes may
span lines.

Leave `var()` and custom function calls unguarded. Both are
declaration values, and `<declaration-value>` admits a balanced curly
block that legally spans lines, as in `--x: --foo({ ... });`. The legal
`--foo({` and the malformed `--foo(a{` are indistinguishable within a
single line, so recovering there would cost legal CSS that main scopes
correctly. Main does not recover an unclosed `var(` either.

Give the `:lang()` string rules the end-of-line fallback
the shared `#string` rule already uses, so an unterminated language
range no longer runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to microsoft#32.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add grammar and regression coverage for modern at-rules, functions,
properties, selectors, and media queries. Include `@container` coverage
for the gap first identified in PR microsoft#15, and accept
digit-prefixed `@property` names consistently with PR microsoft#43.

Dedicated prelude regions end only at `)`, so an unclosed parenthesis
would run to end of file where the generic at-rule header on main
recovers at the first `{`. Guard the parenthesised regions reachable
inside a prelude so they recover at `{` only when the rest of the line
does not close the parenthesis, preserving legal balanced blocks in
declaration values. The test is lexical rather than a plain `[^)]*`,
because a `)` inside a comment, string or escape does not close
anything: without that, `@container (width > 1px{ /* ) */` stayed open
where main recovered. The test also accepts an incomplete trailing
escape, both bare and inside an unterminated string, because a line
ending in an odd number of backslashes otherwise matches no alternative
and the newline-escape rule holds the prelude open. Guarding only the
outermost regions is not enough, because an outer `end` cannot be
evaluated while an inner rule is active. Do not use `;` as a bail-out:
`<general-enclosed>` permits top-level semicolons through `<any-value>`,
and legal preludes may span lines.

Leave `var()` and custom function calls unguarded. Both are declaration
values, and `<declaration-value>` admits a balanced curly block that
legally spans lines, as in `--x: --foo({ ... });`. The legal `--foo({`
and the malformed `--foo(a{` are indistinguishable within a single line,
so recovering there would cost legal CSS that main scopes correctly.
Main does not recover an unclosed `var(` either.

Add `#condition-string` to the `@media` and `@supports` condition
regions. The bail-out only inspects text from the candidate `{` onwards,
so with no string rule active it read the closing quote of `(future:
"a{b")` as an opening one, took the real `)` for shielded, and opened
the body at the brace inside the string. `@container` keeps no string
rule, because there an unterminated string would instead shield a
malformed `{` from the bail-out; that case tokenizes as it already does
on main.

`#condition-string` is a condition-local copy of `#string` rather than
`#string` itself. It differs in one respect: its newline escape ends at
`^` instead of the shared rule's `^(?<!\G)`, which cannot match while
the condition is still open and so swallowed the rest of the stylesheet
after a legal `@media (future: "a{\` continuation. Keeping the copy
local leaves string tokenization everywhere else byte-for-byte as it is
on main.

Give the `:lang()` string rules the end-of-line fallback the shared
`#string` rule already uses, so an unterminated language range no longer
runs past its line.

Leave `animation-timeline`, `animation-range`, `animation-range-start`,
and `animation-range-end` entirely to PR microsoft#32.