action_quit_or_interrupt

Handle Ctrl+C - interrupt agent, reject approval, or quit on double press.

Priority order:

1. If a focused input has a non-empty selection, copy it (a failed copy falls through to the branches below)
2. If shell command is running, kill it
3. If approval menu is active, reject it
4. If ask_user menu is active, cancel it
5. If agent is running, interrupt it (preserve input)
6. If double press (quit_pending), quit
7. If a focused input has text, copy the whole draft (no selection)
8. Otherwise show quit hint

Rapid escape hatch: the clipboard-copy branches (1 and 7) are skipped once Ctrl+C is pressed _RAPID_QUIT_CTRL_C_PRESSES times within _RAPID_QUIT_CTRL_C_WINDOW_SECONDS. Without this, a non-empty draft makes branch 7 copy on every press, so the quit arm is unreachable by Ctrl+C alone. Mashing Ctrl+C then falls through to arm quit (and a further press exits). The interrupt branches (2-5) stay unconditional so a repeated press still cancels in-flight work rather than quitting.