Pitch

The TUI runs in alt-screen, which is great for stable rendering but breaks the terminal's native click-and-drag selection. Users currently can't select arbitrary text the way they would in any other terminal app. Two options:

• A. While Shift is held, temporarily disable mouse capture so the terminal handles selection natively. Release shift → mouse capture resumes.
• B. Add a "Copy mode" (Ctrl+B in tmux's idiom): a keybinding enters a transcript-only state where mouse-drag selects text and Enter copies. Same UX as tmux/screen.

A is more discoverable; B is more powerful. We can ship A in v0.8.6 and consider B for v0.9.

Acceptance

• Shift+drag selects text; release copies via OSC-52 or system clipboard.
• Selection lifetime: shift down → on; shift up → off (mouse capture re-engages).
• No regression for users who never hold shift (default mouse capture behavior unchanged).
• Documented in /help.