## Why
The app server retained its startup model provider for catalog requests, so signing in or out could leave `model/list` using stale provider settings or requiring a restart after managed provider requirements changed.
## What changed
- Invalidate the catalog after successful login and logout, then reload the effective configuration on the next model list or background refresh. Rebuild the models manager when the provider or catalog changes, while preserving existing threads' routes.
- Retain the original project context and the TUI's `--oss` provider selection across reloads. Retry configuration loading after falling back to defaults so temporary failures do not pin the fallback catalog.
- Keep provider policy checks for cached catalogs and apply runtime `api_key_model_discovery` toggles to the active catalog manager.
## Testing
Add and extend tests for provider selection and definition changes after login, catalog reloads after logout, OAuth gateway transitions, fallback recovery, project context, and runtime model discovery toggles.
GitOrigin-RevId: bce2e23ff567e1a52eac2b6ad736a6e63ff61e2b
smurching-oai
7943713993