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/buddy/CompanionCard.tsx

@@ -0,0 +1,109 @@
+/**
+ * Companion display card — shown by /buddy (no args).
+ * Mirrors official vc8 component: bordered box with sprite, stats, last reaction.
+ */
+import React from 'react';
+import { Box, Text } from '../ink.js';
+import { useInput } from '../ink.js';
+import { renderSprite } from './sprites.js';
+import { RARITY_COLORS, RARITY_STARS, STAT_NAMES, type Companion } from './types.js';
+
+const CARD_WIDTH = 40;
+const CARD_PADDING_X = 2;
+
+function StatBar({ name, value }: { name: string; value: number }) {
+  const filled = Math.round(value / 10);
+  const bar = '\u2588'.repeat(filled) + '\u2591'.repeat(10 - filled);
+  return (
+    <Text>
+      {name.padEnd(10)} {bar} {String(value).padStart(3)}
+    </Text>
+  );
+}
+
+export function CompanionCard({
+  companion,
+  lastReaction,
+  onDone,
+}: {
+  companion: Companion;
+  lastReaction?: string;
+  onDone?: (result?: string, options?: { display?: string }) => void;
+}) {
+  const color = RARITY_COLORS[companion.rarity];
+  const stars = RARITY_STARS[companion.rarity];
+  const sprite = renderSprite(companion, 0);
+
+  // Press any key to dismiss
+  useInput(
+    () => {
+      onDone?.(undefined, { display: 'skip' });
+    },
+    { isActive: onDone !== undefined },
+  );
+
+  return (
+    <Box
+      flexDirection="column"
+      borderStyle="round"
+      borderColor={color}
+      paddingX={CARD_PADDING_X}
+      paddingY={1}
+      width={CARD_WIDTH}
+      flexShrink={0}
+    >
+      {/* Header: rarity + species */}
+      <Box justifyContent="space-between">
+        <Text bold color={color}>
+          {stars} {companion.rarity.toUpperCase()}
+        </Text>
+        <Text color={color}>{companion.species.toUpperCase()}</Text>
+      </Box>
+
+      {/* Shiny indicator */}
+      {companion.shiny && (
+        <Text color="warning" bold>
+          {'\u2728'} SHINY {'\u2728'}
+        </Text>
+      )}
+
+      {/* Sprite */}
+      <Box flexDirection="column" marginY={1}>
+        {sprite.map((line, i) => (
+          <Text key={i} color={color}>
+            {line}
+          </Text>
+        ))}
+      </Box>
+
+      {/* Name */}
+      <Text bold>{companion.name}</Text>
+
+      {/* Personality */}
+      <Box marginY={1}>
+        <Text dimColor italic>
+          &quot;{companion.personality}&quot;
+        </Text>
+      </Box>
+
+      {/* Stats */}
+      <Box flexDirection="column">
+        {STAT_NAMES.map(name => (
+          <StatBar key={name} name={name} value={companion.stats[name] ?? 0} />
+        ))}
+      </Box>
+
+      {/* Last reaction */}
+      {lastReaction && (
+        <Box flexDirection="column" marginTop={1}>
+          <Text dimColor>last said</Text>
+          <Box borderStyle="round" borderColor="inactive" paddingX={1}>
+            <Text dimColor italic>
+              {lastReaction}
+            </Text>
+          </Box>
+        </Box>
+      )}
+    </Box>
+  );
+}