fix(tui): address Copilot review comments

- stringWidth: true LRU on cache hit (touch-on-read via delete+set) so
  hot strings stay resident under long sessions; was insertion-order
  FIFO before
- virtualHeights: include todos, panel sections, and intro version in
  messageHeightKey so height-cache reuse correctly invalidates when
  todo content / panel sections change
- virtualHeights: estimate trail+todos rows at todos.length+2 (or 2
  collapsed) instead of the generic ~1-line fallback, so initial
  virtualization offsets are closer to reality
- useInputHandlers: clearTimeout on unmount for scrollIdleTimer so
  pending relaxStreaming() never fires after teardown
- render-node-to-output: drop unused declined.noHint counter from
  scrollFastPathStats; it was always 0 (the "hint missing" branch is
  outside the diagnostics block)
- perfPane / hermes-ink.d.ts: follow the noHint removal
- wheelAccel: replace ~/claude-code path comment with generic
  attribution that doesn't reference a developer-local checkout

ui-tui/src/lib/perfPane.tsx

@@ -132,7 +132,6 @@ export const logFrameEvent = ENABLED
         taken: scrollFastPathStats.taken,
         declined: {
           heightDeltaMismatch: scrollFastPathStats.declined.heightDeltaMismatch,
-          noHint: scrollFastPathStats.declined.noHint,
           noPrevScreen: scrollFastPathStats.declined.noPrevScreen,
           other: scrollFastPathStats.declined.other
         },