v2.3 Phase 5. Provider management lives in Settings → Providers: lists every
registered provider with a status badge, enable/disable toggle (sends the full
override so a custom ACP entry's command survives the wholesale-replace PATCH),
per-provider refresh, and a plaintext diagnostic. The composer provider picker
now filters to enabled && (status==='ready' || 'loading') — disabled/unavailable
providers leave the picker and are managed only in settings; native boocode
always shows. Adds a curated ACP catalog + AddProviderModal (PATCH config then
subset refresh; the modal caps to the viewport with a single overscroll-contain
scroll region). Loading state uses a capped client poll (no WS frame).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
