feat(web): improve model selector with favorites, search, and performance

[leoisadev1]

Summary

• Add favorites system synced to Convex (favoriteModels field in profiles)
• Redesign model selector with T3 Chat-style two-column layout
• Improve search performance and accuracy

Changes

Model Selector Improvements

• Two-column layout: provider sidebar (left) + model list (right)
• Provider sidebar hides when searching for full-width results
• Search uses simple substring match with dash/space normalization
• useDeferredValue for smooth typing during search
• Fix open/close flash by cancelling pending close timeouts
• "Add X suggested" button shows count of missing default models

Favorites System

• New favoriteModels field in profiles table (Convex schema)
• useFavoriteModels hook with optimistic updates
• Default favorites: Claude 4.5, GPT-5.2, Gemini 3, Grok 4.1

Performance

• Disable cmd+k command palette temporarily
• Remove loading states for instant render
• Add localStorage caching for models and chats

Testing

• Verified type checking passes
• Tested model selector open/close/search interactions

[github-actions]

🚀 Preview Deployment Ready

Environment	URL
Frontend	https://web-openchat-pr-490.up.railway.app
Convex Dashboard	Dashboard

Convex Preview Backend

• Cloud URL: https://helpful-husky-251.convex.cloud
• Site URL: https://helpful-husky-251.convex.site

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_{🤖 Deployed automatically by GitHub Actions}

[leoisadev1]

@greptile review