fix(tui): preserve memory monitor in-flight guard

Copilot caught that clearing inFlight on a transient normal-memory tick could
allow a second dump/eviction to start before the first async tick completed.
Only clear dumped on normal; let the in-flight tick's finally remove its own
level.

Tests:
- cd ui-tui && npm run type-check && npm run build

ui-tui/src/lib/memoryMonitor.ts

@@ -68,7 +68,6 @@ export function startMemoryMonitor({
 
     if (level === 'normal') {
       dumped.clear()
-      inFlight.clear()
 
       return
     }