fixtures(google): SPARKLINE conformance rows - #772

115 rows exported from the Google Sheets conformance fixtures, evaluated
against live Sheets across eight probe batches. Every batch after the first
was triggered by a specific finding that could not be settled by argument.

114 of them go to google.tsv. The 115th,
`=MIN(SPARKLINE({1,2,3}),{})` → `#REF!`, is a known engine divergence and
goes to bugs.tsv, this repo's home for GS-captured rows the engine does not
yet match: MIN has no empty-array rule at all, so it answers 0 — for
`=MIN({})` too, with no sparkline involved. `=MAX({})` is `#REF!`, so MAX's
counterpart row passes. The gap predates sparklines and is unrelated to
them; fixing it from here would move MIN for inputs that have nothing to do
with this work. The row is recorded verbatim, so it flips to passing the
moment MIN is fixed and can then move to google.tsv.

The second batch supplied the control the first was missing:
`=SPARKLINE({1,2,3})=SPARKLINE({1,2,3})` → TRUE looked like evidence that a
sparkline's value identity is its parsed spec, but
`=SPARKLINE({1,2,3})=SPARKLINE({9,9,9})` → TRUE disproves it — every
sparkline compares equal to every other. COUNTUNIQUE (2 for different, 1
for identical) is what actually requires the spec to be retained. Two row
descriptions in that batch ("identity: different data is not equal",
"...different charttype is not equal") were written before the run and read
backwards against their own recorded TRUE; the recorded values, not the
descriptions, are the ground truth.

The third and fourth batches settled the currency/conversion split —
DOLLAR and FIXED reject a sparkline while the whole TO_* family answers ""
— plus the single-argument aggregates and the blanket numeric rejection
(ROUND, ABS, INT, unary minus and percent).

The fifth and sixth batches probe a sparkline arriving through a RANGE,
from a cell holding `=SPARKLINE(...)` (`Data!K1`, with 5 in `Data!K2`) —
how a real workbook delivers one. `=PRODUCT(Data!K1:K1)` is 0, so an
aggregate answers the same whichever way the sparkline arrived; the
two-cell rows cannot settle that alone, since 1 × 5 = 5 either way.
`=TYPE(Data!K1)` is 128: reading a cell is not a coercion point, despite
the empty display.

The seventh batch closes the aggregate family: every aggregate answers 0
when a sparkline is the only thing in scope — MAX, MIN, MAXA and MINA
included — with AVERAGE's #DIV/0! the single exception. MINA matching MAXA
was a coin-flip until probed: it had no implementation arm at all.

The eighth batch backs the one direct form that was still being inferred
from its range form (`=MIN(SPARKLINE({1,2,3}))` → 0) and finds a boundary:
an explicitly empty array argument outranks the sparkline skip
(`=MAX(SPARKLINE({1,2,3}),{})` → #REF!) while a text-only array does not
(`=MAX(SPARKLINE({1,2,3}),{"a"})` → 0).

Coverage: each charttype, an omitted charttype, colour options, ymin/ymax,
text inside the data, all-negative data, a genuine blank cell inside a real
source range, `bar` given three values, an unknown option key, an unknown
charttype value, a malformed options shape, the value-model probes, identity
and ordering against sparklines and scalars, the EQ/NE/GTE alias functions,
the three coercion seams, the TO_* family, presence (COUNTA, ISBLANK),
COUNTUNIQUE, and the aggregates direct, through a range, and against empty
and text-only arrays.

69 of google.tsv's 114 SPARKLINE rows are enforced by the conformance
runner. Of the other 45, 29 record an empty expected value (a rendered
chart has no text projection) and 16 read authored input cells the
standalone runner has no workbook to supply — it skips both, and now says
so per file (core#767). crates/core/tests/sparkline.rs asserts those cases
directly, the range rows against a seeded resolver.

One row is deliberately named as a parser artefact: `=SPARKLINE({1,,3})` →
`#ERROR!` is Sheets rejecting the array-literal syntax before SPARKLINE
runs, not a blank-cell rule. The `Data!H`/`Data!I` rows are the trustworthy
blank-cell probe and its all-present control.

Refs #766