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/virtualHeights.ts

@@ -12,8 +12,22 @@ export const hashText = (text: string) => {
   return (h >>> 0).toString(36)
 }
 
-export const messageHeightKey = (msg: Msg) =>
-  [msg.role, msg.kind ?? '', hashText([msg.text, msg.thinking ?? '', msg.tools?.join('\n') ?? ''].join('\0'))].join(':')
+export const messageHeightKey = (msg: Msg) => {
+  const todoSig = msg.todos?.map(t => `${t.status}:${t.content}`).join('\u0001') ?? ''
+  const panelSig =
+    msg.panelData?.sections
+      .map(s => `${s.title ?? ''}:${s.text?.length ?? 0}:${s.items?.length ?? 0}:${s.rows?.length ?? 0}`)
+      .join('\u0001') ?? ''
+  const introSig = msg.kind === 'intro' ? (msg.info?.version ?? '') : ''
+
+  return [
+    msg.role,
+    msg.kind ?? '',
+    hashText(
+      [msg.text, msg.thinking ?? '', msg.tools?.join('\n') ?? '', todoSig, panelSig, introSig].join('\0')
+    )
+  ].join(':')
+}
 
 export const wrappedLines = (text: string, width: number) => {
   const w = Math.max(1, width)
@@ -34,6 +48,14 @@ export const estimatedMsgHeight = (
     return Math.max(3, (msg.panelData?.sections.length ?? 1) * 2 + 1)
   }
 
+  if (msg.kind === 'trail' && msg.todos?.length) {
+    if (msg.todoCollapsedByDefault) {
+      return 2
+    }
+
+    return Math.max(2, msg.todos.length + 2)
+  }
+
   const bodyWidth = Math.max(20, cols - 5)
   const text = msg.role === 'assistant' && limitHistory ? boundedHistoryRenderText(msg.text) : msg.text
   let h = wrappedLines(text || ' ', bodyWidth)