fix(lock): compare the tail check against the stored chained promise

[latent-9]

withLock stores prev.then(() => next) in the locks table, but the cleanup compares locks.get(key) against next. The map never holds next (it holds the promise returned by .then), so the tail check is always false and the entry is never deleted. The comment says avoid unbounded growth, but the cleanup is dead: locks grows by one entry per distinct key for the process lifetime. The write path takes a keyed lock per namespace and per owner, and the section can throw before the map is trimmed, so entries leak even for rejected requests. Reachable from PUT/DELETE /api/memory/:ns via upsert. Fix: compare against the chained promise that is actually stored. Adds tests for serialization, drain-to-empty across many keys and under contention, and cleanup on throw; the drain and throw cases fail on the old code and pass with the fix. Full suite green, 61 tests.

[kevincodex1]

looks good to me

[kevincodex1]

hello @latent-9 thank you for your contribution some test is failing please fix the formatting.

[latent-9]

@kevincodex1 Thanks for taking a look. That failure was Biome's import sorting on the new test file: the named imports in tests/lock.test.ts were not alphabetical, so biome ci bailed before the tests ran. I sorted them and re-ran the checks locally, biome ci is clean, type-check passes, and all 61 tests pass. Pushed the fix.