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/packages/hermes-ink/src/ink/terminal.ts

@@ -289,9 +289,7 @@ export function writeDiffToTerminal(
   // The 2-arg form attaches a drain callback that fires once the chunk
   // is actually flushed to the OS socket/pipe — giving us end-to-end
   // drain timing, not just "queued in Node".
-  const wrote = onDrain
-    ? terminal.stdout.write(buffer, () => onDrain())
-    : terminal.stdout.write(buffer)
+  const wrote = onDrain ? terminal.stdout.write(buffer, () => onDrain()) : terminal.stdout.write(buffer)
 
   return { bytes: Buffer.byteLength(buffer, 'utf8'), backpressure: !wrote }
 }