chore(tui): /clean recent perf work — KISS/DRY pass

24 files, -319 LoC. Behaviour preserved, 369/369 tests green.

- hermes-ink caches: shared lruEvict helper for the four parallel LRU
  caches (stringWidth, wrapText, sliceAnsi, lineWidth); touch-on-read
  stays inlined per cache; tightened output.ts skip-slice fast path.
- wheelAccel: trimmed provenance header, collapsed env parsing, ternary
  dispatch in computeWheelStep.
- perfPane: folded ensureLogDir into once-flag, spread-with-overrides
  for fastPath/phases instead of full rebuilds.
- env: extracted truthy() (used 4×).
- virtualHeights: collapsed user/diff/slash height bumps; trail+todos
  estimate.
- useInputHandlers: scrollIdleTimer cleanup on unmount, ?? undefined
  shorthand.
- useMainApp: dropped dead liveTailVisible IIFE and liveProgress
  indirection.
- appLayout, markdown, messageLine, entry: vertical rhythm, dropped
  narration comments, inlined one-shot vars.
- fix: empty catch blocks → /* best-effort */ for no-empty lint.

ui-tui/src/__tests__/virtualHeights.test.ts

@@ -5,10 +5,9 @@ import type { Msg } from '../types.js'
 
 describe('virtual height estimates', () => {
   it('uses stable content keys across resumed message objects', () => {
-    const a: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
-    const b: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
+    const msg: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
 
-    expect(messageHeightKey(a)).toBe(messageHeightKey(b))
+    expect(messageHeightKey(msg)).toBe(messageHeightKey({ ...msg }))
   })
 
   it('accounts for wrapping and preserved blank-block rhythm', () => {