Resuming a long session (196k events, 2.2k steps, 1.8k tool cards) took
~12s to render and ~800ms to echo one keystroke:
- Every step's timing footer called stepTimingAt, which replayed the whole
event log per footer - O(steps x events) on the initial render.
- pi-tui re-renders every component each frame and relies on per-component
line caches, but ToolCardComponent/ContextCardComponent built throwaway
Text/Markdown instances inside render(width), re-wrapping every settled
card's output on every keystroke.
Replace the per-footer replay with one shared StepTimingTracker per chat
mount (single O(events) cursor over the append-only log), and cache card
rows by width via CardLineCache, dropped by every state mutator and
invalidate().
Measured (tmux 200x50, 196k-event session): resume prompt-ready ~12s -> ~7.6s;
per-keystroke echo ~800ms median -> ~11ms.
Extract model-command, questions, and resume sub-machines from the
~1600-line createTuiChat closure into src/chat/ factories that take
explicit dependency bundles (shared ChatChannelDeps/ChannelNotice).
Reorganize src/ so chat/ holds all chat-channel concerns (former input
and session/ files move under it); xml-tool-output moves to components/;
TuiRuntime/TuiResumeHost move to runtime.ts. index.ts drops 2067->~1530
lines. Behavior identical: 167 tests and all TUI snapshots pass unchanged.
