Add embedded React web UI

[jdfalk]

Summary

• implement React SPA in webui/ built with Vite
• embed built assets and expose via web command
• document web UI plans and usage
• describe build steps in technical design

Testing

• go test ./...

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https://chatgpt.com/codex/tasks/task_e_6843901486688321abcec26a93a7b2d9

[github-actions]

Rollback mechanisms need further investigation:

🔄 Partial support:

• Dry-run mode for testing
• Failed operations don't affect successful ones (matrix strategy)
• Files remain in place if processing fails

❌ Still needed:

• Transaction support for multi-step operations
• Explicit rollback for partially completed operations
• State persistence for recovery

This aligns with TODO.md Phase 2 improvements. Should remain open.

[github-actions]

Rollback mechanisms need further investigation:

🔄 Partial support:

• Dry-run mode for testing
• Failed operations don't affect successful ones (matrix strategy)
• Files remain in place if processing fails

❌ Still needed:

• Transaction support for multi-step operations
• Explicit rollback for partially completed operations
• State persistence for recovery

This aligns with TODO.md Phase 2 improvements. Should remain open.