* feat: multi-model health tracking with runtime default and DB-only startup
Replace active-probe circuit breaker with passive per-backend health
tracking. Backends are marked degraded after consecutive failures and
recover when a request succeeds — requests are never blocked.
- Add model.default_alias ConfigStore setting for runtime default model
- Make load_model_registry CLI args optional for DB-only startup
- Per-(provider, base_url) health trackers via HealthTrackerRegistry
- Two-pass fallback: prefer healthy backends, then try degraded
- Remove BackendHealthMonitor, CircuitState, probe threads, cooldown
- Remove circuit_state from API schema, SDK events, metrics, frontends
* feat: add "Set Default" button to Model Definitions admin panel
Show a "default" badge on the current default model alias and a
"set default" action button on all other models. Clicking it writes
model.default_alias via the settings API. The list endpoint now
includes default_alias in the response so the UI can highlight it.
* fix: address review feedback — metric scoping, effective default, session alias
- Move turnstone_backend_up metric out of BackendHealthTracker into
server callback; only the effective default backend drives the gauge
- _build_health_dict resolves effective default via ConfigStore override
- session_factory computes selected_alias once before registry.resolve
- admin model-definitions endpoint returns effective default (not just
override) so UI shows correct badge when ConfigStore is empty
- Rename circuitTitle → healthTitle in console JS
- Fix ruff SIM117 lint in test
* fix: validate effective default against enabled models, degraded label, log normalization
- admin model-definitions endpoint validates default_alias against
enabled models using same fallback rules as load_model_registry
- UI text "backend down" → "backend degraded" to match advisory semantics
- Health tracker log uses normalized base_url from key, not raw argument
Patrick Buckley
2b93598d68