…184)

StringId is enum class : uint32_t, so < on it was the built-in enum comparison:
interning order. Whether a given comparison meant "handle order, because this is
a set" or "name order, because this order is observable" was untyped, unstated,
and spelled with the same character. Four bugs came out of that confusion --
and wrongly cleared in PR #176's own description.

The relational operators are now deleted. A user-declared deleted operator wins
overload resolution over the built-in candidate for a scoped enum, so every
comparison site had to be visited and state which order it means: handle_less for
a set, or a pool projection for anything a person or another build can observe.
Equality is untouched.

The compiler found 21 sites. Eighteen were genuine set structures and now say so.
Three were ordering bugs:

  src/exec/scheduler.cpp:62 (fixes #183) -- the env cache was sorted by handle and
  binary-searched by name at :44, so lower_bound's precondition was violated and
  lookups missed variables that were present. prepare_job_launch then omitted
  them and, since base_child_env contributes only PATH=, they were absent from
  the child entirely. Three exports declared in reverse-lexicographic order lost
  all three, silently, exit 0.

  src/cli/context.cpp:677 (fixes #184) -- cached_env_vars was sorted by handle and
  binary-searched by name at builder.cpp:1305. A missed lookup falls through to an
  empty value, so an imported variable lost its cached value on the next build,
  changing rendered command text and therefore command identity.

  src/parser/var_tracking.cpp:21 -- group_by_name ordered by handle despite its
  name, and the show-var command prints the result. Now ordered by name, which
  changes that command's output order.

src/core/layout.cpp:221 is fixed here too because it will not compile otherwise;
that is the same one-line change as PR #176, which can land either before or
after this.

No INDEX_VERSION bump: no persisted format changes and no deliberate identity
semantics change. Commands whose identity was computed from a wrongly-empty env
value will re-run once, which is the intended repair.

Both bugs were reproduced before the fix and re-checked after:

  export ZVAR/MVAR/AVAR   before: 0 of 3 in child env   after: 3 of 3
  import Z/M/A, rebuild   before: A= M= Z=              after: A=aaa M=mmm Z=zzz

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TLob4Ef3qyMd3Dnp9q3XmA