search/: sliding-window matcher over pages, active-area, page list,
viewport and screen searches, and the background search thread (std
thread + crossbeam-channel mailbox, 24 ms refresh, terminal behind
Arc<Mutex<_>>). Searches take &mut Screen explicitly; ScreenSearch::deinit
must be called to untrack pins. The sliding window uses a VecDeque
instead of CircBuf (same results; two layout-only assertions dropped).
tmux/: layout parsing, output formatting and the control-mode viewer
state machine, reusing ghostty_vt::tmux::control for parsing. The viewer
is not wired into termio yet; steps are in the notes.
The renderer must set terminal.flags.search_viewport_dirty for the
search thread to re-search the viewport.
Test Plan:
- cargo test -p ghostty-terminal --lib search (54; 51/53 Zig tests,
2 allocator-failure tests skipped)
- cargo test -p ghostty-terminal --lib tmux (96; all Zig tests)
