CodSpeed attribution (zero-diff control #2906 clean; single-patch probes
#2907/#2908/#2909): the config-brand change alone carries merge -7%
plus sub-threshold -3..4% across update1to1/propagation — it drove both
flagged regressions on this PR. The diff is load-neutral by inspection
and byte-flat in an isolated merge harness; the diffuse cross-bench
pattern indicates shared-process JIT/IC state redistribution from the
hasOverride shape change. Pulled pending a shape-stable redesign
(dedicated boolean in the node literal rather than a _config RMW).

Remaining: pending-container + ambient-txn, both CodSpeed-clean in
isolation. Full 57,073->56,550 min / 21,229->21,050 gz; floor
18,551->18,111 / 7,527->7,376. 1,052 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

…audit (#2905)

* refactor(signals): tier-2 state consolidations from the architecture audit

Three behavior-preserving consolidations, each retiring a bug class:

- single pending-source container: the _pendingSource/_pendingSources
  dual representation (singular slot + lazily-promoted Set) collapses to
  one lazily-created Set; the promotion invariant #2893's first bug
  broke no longer exists. -267 min / -110 gz.
- optimistic brand as CONFIG_OPTIMISTIC bit: deletes OVERRIDE_UNDEFINED
  and 19 wrap/unwrap sites; the undefined-as-value / undefined-as-brand
  collision (#2898) is unrepresentable. -123 / -26.
- ambient work is a transaction: the globalQueue's parallel batch fields
  and initTransition's four adoption/aliasing blocks collapse into one
  always-present batch shape; flush fast-path emptiness check preserved.
  -270 / -96.

Combined: full 57,073->56,413 min / 21,229->21,008 gz; floor
18,551->18,013 / 7,527->7,357. 1,052 tests pass on the integrated
branch; each patch was independently verified (byte-exact re-measurement,
suite re-run via poison-probed alias configs, hunk-by-hunk behavior
review) before integration.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* perf(signals): restore write-path load count with a module-local batch mirror

CodSpeed flagged updateSignals:update1to1 at -6.8% on #2905 (reproduced
on rerun): queuePendingNode gained a property hop when the batch fields
moved behind globalQueue._batch, and it runs once per staged write.
A module-local mirror updated at the three _batch assignment sites
restores the pristine load count on the write path and commit loop; the
field stays authoritative for cross-module readers.

The merge bench regression is not yet attributed — this push doubles as
the bisection probe: if it persists, it belongs to the pending-container
or config-brand change, not the batch consolidation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* revert(signals): pull the config-brand consolidation from this PR

CodSpeed attribution (zero-diff control #2906 clean; single-patch probes
#2907/#2908/#2909): the config-brand change alone carries merge -7%
plus sub-threshold -3..4% across update1to1/propagation — it drove both
flagged regressions on this PR. The diff is load-neutral by inspection
and byte-flat in an isolated merge harness; the diffuse cross-bench
pattern indicates shared-process JIT/IC state redistribution from the
hasOverride shape change. Pulled pending a shape-stable redesign
(dedicated boolean in the node literal rather than a _config RMW).

Remaining: pending-container + ambient-txn, both CodSpeed-clean in
isolation. Full 57,073->56,550 min / 21,229->21,050 gz; floor
18,551->18,111 / 7,527->7,376. 1,052 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>