The slow-request journal showed /api/profiles, /api/models, and /api/session
fire on every session click but had no per-stage timing. Add:
- RequestDiagnostics coverage for GET /api/profiles, /api/models, /api/session
- Stage markers inside /api/profiles (list / active lookup / isolated check)
- Stage markers inside /api/models (freshness routing, serialize)
- Per-stage stage-log inside get_available_models_for_session_visit that
emits a [SLOW] line when total wall time crosses HERMES_DEBUG_SLOW ms
(default 500ms) so we can pinpoint which sub-step is blocking
No behavior change. Existing _t0.._t6 timing on /api/session and the
2.5s/10s TTL on /api/sessions are unchanged. Reversible: revert commit.
A threading.Timer per RequestDiagnostics spawns one OS thread per request, held
alive until finish() cancels it. Under sustained /api/sessions poll load this
exhausts the per-process thread cap (RuntimeError: can't start new thread) and
the server stops accepting connections. Replace with a single lazy-init
watchdog daemon thread that scans pending diags every ~1s; public API
unchanged. Caps timeout-tracking at 1 thread/process regardless of request rate.
