lint-allow-test-rule-refs (ADR-456) flagged the two architectural-invariant
exemptions as novel offenders lacking a #NNN reference, failing lint-tests. Add
(see #1531) to both annotation lines; lint:ci now green.
Claude-Session: https://claude.ai/code/session_01R88n7Q54bAaVHFkDbbH1yz
Root cause: writeStateMd computed its frontmatter disk scan
(syncStateFrontmatter — the READ half of a read-modify-write) BEFORE
acquireStateLock, leaving a TOCTOU window. A concurrent writer that
committed a new PLAN/SUMMARY between our scan and our lock made writeStateMd
stamp stale progress counts (lost update — the #500/#905/#1230 family). The
atomic sibling readModifyWriteStateMd already scans inside its lock.
Fix: move _diskScanCache.delete + syncStateFrontmatter inside the
acquireStateLock-held try, before platformWriteSync. Byte-for-behaviour
identical for single-threaded callers — only the concurrent-writer window
closes. Adds an afterAcquire test seam (mirrors the M1 _setLockProbes seam)
to make the window deterministic; new test proves RED (stale count) before
the reorder and GREEN after.
Source of truth src/state.cts (ADR-457); bin/lib/state.cjs is generated.
Claude-Session: https://claude.ai/code/session_01R88n7Q54bAaVHFkDbbH1yz
