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/packages/hermes-ink/src/ink/render-node-to-output.ts

@@ -79,7 +79,6 @@ export type ScrollFastPathStats = {
   declined: {
     noPrevScreen: number
     heightDeltaMismatch: number
-    noHint: number
     other: number
   }
   lastDeclineReason?: string
@@ -95,7 +94,6 @@ export const scrollFastPathStats: ScrollFastPathStats = {
   declined: {
     noPrevScreen: 0,
     heightDeltaMismatch: 0,
-    noHint: 0,
     other: 0
   }
 }
@@ -105,7 +103,6 @@ export function resetScrollFastPathStats(): void {
   scrollFastPathStats.taken = 0
   scrollFastPathStats.declined.noPrevScreen = 0
   scrollFastPathStats.declined.heightDeltaMismatch = 0
-  scrollFastPathStats.declined.noHint = 0
   scrollFastPathStats.declined.other = 0
   scrollFastPathStats.lastDeclineReason = undefined
   scrollFastPathStats.lastHeightDelta = undefined