perf(tui): incremental step timing and card render caches for long sessions

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.

docs/cordis-catalog/services.md

@@ -2451,7 +2451,7 @@ The concrete provider retains pi-tui, focus, and terminal lifecycle state. Plugi
 abstract openOverlay(request: TuiOverlayRequest): TuiOverlaySession
 ```
 
-Source: [`packages/ui/tui/src/index.ts:245`](../../packages/ui/tui/src/index.ts)
+Source: [`packages/ui/tui/src/index.ts:246`](../../packages/ui/tui/src/index.ts)
 
 ## `ctx.typert` — `TypertRegistry`