v3.0.0: Phase 3 complete — autonomous agent system

Fully working end-to-end autonomous project mode:
- Qwen-3.6 drafts plan + permission manifest
- User approves once; codec-agent-runner executes autonomously
- Live checkpoint updates stream into the chat thread
- Messages persist across page reloads
- Project folder created for every task, output files listed on completion
- '📂 Open folder' and '📄 View files' buttons in done message
- Chat history delete (trash icon in sidebar)
- Global read grants for ~/codec-repo/**
- File-iteration state injection prevents Qwen batching 30-file tasks
- JSON truncation recovery with automatic retry
- read_paths glob pattern fixed (**/*.ext → /**)

Anchor example: 'Read all markdown files in ~/codec-repo/docs/ and create
an index.md' — completed autonomously in 2 checkpoints, 15 steps.