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/app/useInputHandlers.ts

@@ -1,6 +1,6 @@
 import { useInput } from '@hermes/ink'
 import { useStore } from '@nanostores/react'
-import { useRef } from 'react'
+import { useEffect, useRef } from 'react'
 
 import { TYPING_IDLE_MS } from '../config/timing.js'
 import type {
@@ -40,6 +40,16 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
   // as the BASE — final rows = wheelStep × accelMult.
   const wheelAccelRef = useRef(initWheelAccelForHost())
 
+  useEffect(
+    () => () => {
+      if (scrollIdleTimer.current) {
+        clearTimeout(scrollIdleTimer.current)
+        scrollIdleTimer.current = null
+      }
+    },
+    []
+  )
+
   const scrollTranscript = (delta: number) => {
     if (getUiState().busy) {
       turnController.boostStreamingForScroll()