configurable kg / meeting / track-block model overrides

Bring back per-category model selection that 5c4aa772 dropped, plus add a
new track-block category. Each is a BYOK-only override on `LlmModelConfig`
(`knowledgeGraphModel`, `meetingNotesModel`, `trackBlockModel`); signed-in
users always get the curated gateway default and never hit the on-disk
config.

Three helpers in core/models/defaults.ts — `getKgModel`,
`getTrackBlockModel`, `getMeetingNotesModel` — each check `isSignedIn`
first (fast path) and fall through to `cfg.<field> ?? cfg.model` for BYOK.

The model is now picked at the invocation site rather than via runtime
agent-name branching: each top-level `createRun` for a polling KG agent
or a track-block update passes `model: await getXxxModel()`. The `model:`
declarations on the affected agent YAMLs are dropped — they were dead
code under the per-call override. Standalone (non-run) callers
`track/routing` and `summarize_meeting` use the helpers inline.

Settings dialog and the two onboarding flows surface the two new fields
("Meeting Notes Model", "Track Block Model") next to the existing
"Knowledge Graph Model"; `repo.setConfig` persists all three per-provider.

Note: the signed-in `RowboatModelSettings` panel still has its
now-defunct kg selector; that's a UI cleanup for a later pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/x/packages/shared/src/models.ts

@@ -18,8 +18,9 @@ export const LlmModelConfig = z.object({
     model: z.string().optional(),
     models: z.array(z.string()).optional(),
   })).optional(),
-  // Deprecated: per-run model+provider supersedes these. Kept on the schema so
-  // existing settings/onboarding UIs continue to compile until they're cleaned up.
+  // Per-category model overrides (BYOK only — signed-in users always get
+  // the curated gateway defaults). Read by helpers in core/models/defaults.ts.
   knowledgeGraphModel: z.string().optional(),
   meetingNotesModel: z.string().optional(),
+  trackBlockModel: z.string().optional(),
 });