feat: add TUI dialog for interactive YOLO mode selection

[hunterd]

Summary

Adds an interactive TUI dialog that opens when typing /yolo without arguments, showing the current mode and letting the user switch between Off / On / Aggressive directly — without going through the agent.

Changes

• New tui.ts — TUI plugin entry point (@frankhommers/opencode-yolo/tui):
  • Registers a /yolo slash command via api.command.register()
  • Reads .yolo.json synchronously to determine the current mode
  • Shows a DialogSelect with the current mode pre-selected (● indicator)
  • Writes .yolo.json on selection and closes the dialog
• package.json — Added "./tui" export subpath
• tsconfig.json — Added tui.ts to the build include list
• README.md — Updated with TUI plugin install instructions, dialog screenshot, and development notes

How it looks

┌─────────────────────────────┐
│  YOLO Mode — On        esc  │
├─────────────────────────────┤
│ ○ Off  Require manual ...   │
│ ● On   Currently active...  │
│ ○ Aggressive Auto-approve…  │
└─────────────────────────────┘

The active mode is shown in the dialog title (YOLO Mode — Off / On / Aggressive) and marked with ● in the list with a "Currently active — …" description.

Notes

• The TUI plugin is a separate entry point that does not depend on the hooks plugin
• It uses synchronous fs APIs (appropriate for the TUI rendering context)
• The dialog closes automatically after selecting a mode
• Accessible also via Ctrl+P → search "yolo"

Closes #(add issue if any)