Lifts `handle_paste_burst_key`, `handle_paste_burst_decision`,
`apply_paste_burst_retro_capture`, and the local `in_command_context`
helper out of `tui/ui.rs` into a sibling module. The state machine
(`PasteBurst`) and its tests stay in `paste_burst.rs`; only the keymap-
side wiring moves. Drops the now-unused `CharDecision` import from
`ui.rs`.
Workspace tests: 1011/1011 still green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Hunter Bown
56308bb5d7