039 — Unify useCaps on usePolledReader<Caps>

[archae0pteryx]

039 — Unify useCaps on usePolledReader<Caps>

What to build

useCaps (src/hooks/useCaps.ts) is a one-shot reader pattern: returns Caps directly, silently falls back to DEFAULT_CAPS on error, no loading state. useFocuses and useProposals (now collapsed in 037/038) use the polled pattern: loading | ready | error. Two patterns for the same job.

Unify on usePolledReader<Caps>. Preserve current UX (silent default fallback, no loading flash) by mapping the polled state at the call site.

Changes

• src/api/caps.ts — CapsReader becomes PolledReader<Caps>. get() renames to read(). Drop the subscribe? field if caps are not pushed by Tauri (currently they are not — caps are read once at startup).
• src/api/caps.ts — createTauriCapsReader and createFixtureCapsReader return PolledReader<Caps>.
• src/hooks/useCaps.ts — delete.
• src/hooks/useAppState.ts (line 30) — replace useCaps(capsReader) with:

  const capsState = usePolledReader<Caps>(capsReader);
  const caps = capsState.status === "ready" ? capsState.value : DEFAULT_CAPS;

• useAppState re-exports caps: Caps to match the current consumer contract — no downstream component needs to handle a loading/error variant.

Behavior contract

• Silent fallback to DEFAULT_CAPS on error preserved.
• Caps surface to consumers as Caps, not as a polled state. (Other catalogs surface the full polled state because they need to render loading/empty UI; caps drive only badge thresholds where defaults are correct.)

Out of scope

• Pushing live cap-config updates from Tauri (would need subscribe); caps still load once at startup.
• Generic factory (040).

Completion promise

useCaps no longer exists. Caps load through usePolledReader<Caps>; the silent-default UX is preserved by collapsing the polled state to Caps inside useAppState.

Acceptance criteria

• CapsReader is PolledReader<Caps> (or aliased to it).
• src/hooks/useCaps.ts deleted.
• useAppState uses usePolledReader<Caps> and falls back to DEFAULT_CAPS on non-ready states.
• No component receives a loading or error state for caps; consumer contract unchanged.
• Existing cap-badge tests still green.
• task check green.

Blocked by

037 — establish the rename and call-site pattern in the simpler Focus pipeline first.