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

ui-tui/packages/hermes-ink/src/ink/stringWidth.ts

@@ -311,13 +311,16 @@ export const stringWidth: (str: string) => number = str => {
   const cached = widthCache.get(str)
 
   if (cached !== undefined) {
+    // True LRU: refresh recency by re-inserting (Map iteration is insertion order).
+    widthCache.delete(str)
+    widthCache.set(str, cached)
+
     return cached
   }
 
   const w = rawStringWidth(str)
 
   if (widthCache.size >= WIDTH_CACHE_LIMIT) {
-    // Drop oldest entry — Map iteration order is insertion order.
     widthCache.delete(widthCache.keys().next().value!)
   }
 

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()

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
         },

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)

ui-tui/src/lib/wheelAccel.ts

@@ -1,9 +1,8 @@
 // Wheel-scroll acceleration state machine.
 //
-// Ported from claude-code's src/components/ScrollKeybindingHandler.tsx
-// (commit cb7cfba6 of their research snapshot at ~/claude-code).  The
-// algorithm is theirs; the tuning constants below are theirs; this file
-// is a straight port adapted to our module structure.
+// Algorithm and tuning constants adapted from a reference implementation
+// of trackpad/wheel-event acceleration in TUI scroll handlers; this file
+// is the port adapted to our module structure.
 //
 // Problem: one wheel event = 1 scrolled row feels sluggish on trackpads
 // (which can fire 200+ events/sec) and during deliberate mouse scrolls.

ui-tui/src/types/hermes-ink.d.ts

@@ -112,7 +112,6 @@ declare module '@hermes/ink' {
     declined: {
       noPrevScreen: number
       heightDeltaMismatch: number
-      noHint: number
       other: number
     }
     lastDeclineReason?: string