chore: remove dead code command-input.tsx (376 lines)

Component was exported but never imported/used anywhere.
v3.0 architecture uses chat-input.tsx instead.

Voice features (useCortexVoice hook) remain available for future use.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

components/cortex/command-center/index.ts

@@ -3,7 +3,6 @@
  */
 
 export { CommandCenter } from './command-center';
-export { CommandInput } from './command-input';
 export { ContextBar } from './context-bar';
 export { CanvasArea } from './canvas-area';
 export { RecentStrip } from './recent-strip';