Testing: Nightly workflow (T-11) #345

Part of the test strategy (captain, 2026-10-05: scenarios that test the changes together; cleaner, faster suites; TESTING.md). Epic #305.

Scope. nightly.yml: INPUTLAYER_ORACLE_SEEDS=300, INPUTLAYER_SOAK=1 soak (#298: 10 min, oracle-checked histories with 200 subscribers and slow consumers), cargo fuzz parser and WS frames for 10 min each (#301), the HNSW recall test with the level-scale fix (#302) and brute-force recall over 3 sizes, perf-gate-remote.sh on the bench host under the shared lock (PR 273), coverage once a week; results posted as a job summary; a nightly failure opens or updates one tracking issue.

Acceptance. First nightly green or with named XFAILs; the perf gate report lands in the summary; #[ignore] count stays zero.