refactor(buddy): align companion system with official CLI

## Summary

Reverse-engineered the official Claude Code CLI (v2.1.91) buddy/companion
system and aligned our implementation to match.

## Changes (7 files)

### Added
- `src/buddy/CompanionCard.tsx` (+109)
  JSX bordered card matching official vc8: rarity header, colored sprite,
  name, personality, 10-bar stats, last reaction in nested border.

- `src/buddy/companionReact.ts` (+156)
  Reaction system matching official ZUK+Dc8: 45s rate limiting, @-mention
  detection, transcript builder (12 msgs, 5000 chars), POST buddy_react API.

### Modified
- `src/commands/buddy/index.ts`
  type: local -> local-jsx, description/argumentHint/immediate/isHidden.

- `src/commands/buddy/buddy.ts`
  LocalCommandCall -> LocalJSXCommandCall signature (onDone, context, args).
  Removed mute/unmute/rehatch (official uses off/on only).
  /buddy show returns CompanionCard JSX instead of plain text.
  Pet auto-unmutes. companionMuted writes globalConfig (matches UI read source).

- `src/screens/REPL.tsx` (line 2808)
  globalThis.fireCompanionObserver -> import triggerCompanionReaction.

- `src/state/AppStateStore.ts` — comment fix.
- `src/types/global.d.ts` — removed fireCompanionObserver declaration.

## Data flow (verified consistent)
- companionMuted: saveGlobalConfig() <-> getGlobalConfig() (6 read sites)
- companionReaction: setAppState() <-> useAppState() (4 sites)
- companionPetAt: setAppState() <-> useAppState() (2 sites)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/state/AppStateStore.ts

@@ -165,7 +165,7 @@ export type AppState = DeepImmutable<{
   foregroundedTaskId?: string
   // Task ID of in-process teammate whose transcript is being viewed (undefined = leader's view)
   viewingAgentTaskId?: string
-  // Latest companion reaction from the friend observer (src/buddy/observer.ts)
+  // Latest companion reaction from buddy_react API (src/buddy/companionReact.ts)
   companionReaction?: string
   // Timestamp of last /buddy pet — CompanionSprite renders hearts while recent
   companionPetAt?: number