Add TUI for managing sandbox profile, relicense to GPLv3
- Add Go/Bubble Tea TUI app under tui/ with dashboard (status checks,
launch, validate) and profile editor (commands, filesystem, network,
environment sub-tabs)
- Add Makefile targets: tui, tui-build, tui-install
- Add CI step to build TUI
- Relicense MIT -> GPL-3.0
- Rewrite wrapper to resolve real opencode binary from PATH (supports
brew, npm, volta)
- Add PATH ordering detection to install script
- Expand README with how-it-works diagram, TUI docs, keybinding table