fix(tui): address PR #13231 review comments

Six small fixes, all valid review feedback:

- gatewayClient: onTimeout is now a class-field arrow so setTimeout gets a
  stable reference — no per-request bind allocation (the whole point of
  the original refactor).
- memory: growth rate was lifetime average of rss/uptime, which reports
  phantom growth for stable processes. Now computed as delta since a
  module-load baseline (STARTED_AT). Sanity-checked: 0.00 MB/hr at
  steady-state, non-zero after an allocation.
- hermes_cli: NODE_OPTIONS merge is now token-aware — respects a
  user-supplied --max-old-space-size (don't downgrade a deliberate 16GB
  setting) and avoids duplicating --expose-gc.
- useVirtualHistory: if items shrink past the frozen range's start
  mid-freeze (/clear, compaction), drop the freeze and fall through to
  the normal range calc instead of collapsing to an empty mount.
- circularBuffer: throw on non-positive capacity instead of silently
  producing NaN indices.
- debug slash help: /heapdump mentions HERMES_HEAPDUMP_DIR override
  instead of hardcoding the default path.

Validation: tsc clean, eslint clean, vitest 102/102, growth-rate smoke
test confirms baseline=0 → post-alloc>0.

ui-tui/src/hooks/useVirtualHistory.ts

@@ -124,14 +124,17 @@ export function useVirtualHistory(
   const vp = Math.max(0, scrollRef.current?.getViewportHeight() ?? 0)
   const sticky = scrollRef.current?.isSticky() ?? true
 
-  const frozenRange = freezeRenders.current > 0 ? prevRange.current : null
+  // During a freeze, drop the frozen range if items shrank past its start
+  // (/clear, compaction) — clamping would collapse to an empty mount and
+  // flash blank. Fall through to the normal path in that case.
+  const frozenRange =
+    freezeRenders.current > 0 && prevRange.current && prevRange.current[0] < n ? prevRange.current : null
 
   let start = 0
   let end = n
 
   if (frozenRange) {
-    // Clamp in case items shrank (/clear, compaction) mid-freeze.
-    start = Math.min(frozenRange[0], n)
+    start = frozenRange[0]
     end = Math.min(frozenRange[1], n)
   } else if (n > 0) {
     if (vp <= 0) {