feat: add mode system with 6 AI personality presets (#1255)

* docs: update contributors

* docs: update contributors

* feat: add mode system with 6 AI personality presets

Add a /mode command that lets users switch between 6 interaction
modes, each with distinct system prompts, UI themes, permission
defaults, and response verbosity:

- Default (⚡) — balanced, everyday development
- Gentle (🌸) — patient explanations for learning
- Dr. Sharp (🔍) — strict 3-phase code review workflow
- Workhorse (🐴) — auto-execute, minimal confirmations
- Token Saver (💰) — minimal replies to save tokens
- Super AI (🧠) — deep analysis, proactive suggestions

Custom modes can be defined via YAML files in ~/.claude/modes/.

New files:
- src/modes/types.ts — CCBMode interface
- src/modes/defaults.ts — 6 built-in mode presets
- src/modes/store.ts — mode state management with useSyncExternalStore
- src/commands/mode/index.ts — command registration
- src/commands/mode/mode.tsx — mode picker UI

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

src/commands.ts

@@ -19,6 +19,7 @@ import { context, contextNonInteractive } from './commands/context/index.js'
 import diff from './commands/diff/index.js'
 import doctor from './commands/doctor/index.js'
 import memory from './commands/memory/index.js'
+import mode from './commands/mode/index.js'
 import help from './commands/help/index.js'
 import ide from './commands/ide/index.js'
 import init from './commands/init.js'
@@ -327,6 +328,7 @@ const COMMANDS = memoize((): Command[] => [
   mcp,
   memory,
   mobile,
+  mode,
   model,
   outputStyle,
   remoteEnv,