Find & Fix Memory Leaks & Retain Cycles

Background: Native [platform] app, [SwiftUI+Combine / Compose]. Symptom:
[memory grows over time / app killed in background / a screen's objects
never deallocate]. Suspect area: [screen/feature, or "unknown"].

Use case: Find the leak/retain cycle and fix it.

Implementation details:
- iOS: use Leaks/Allocations and the memory graph debugger; the usual
  culprits—strong self in closures (use [weak self]), Combine
  subscriptions not stored/cancelled, delegate cycles, captured view
  models. Android: LeakCanary and the memory profiler; culprits—leaked
  Contexts/Activities, uncancelled coroutines/collectors, listeners not
  removed, static references.
- Confirm the leak with the tool before fixing (don't guess)
- Verify objects deallocate after the screen is dismissed
- Distinguish a true leak from expected caching/high-water memory

Deliverable: The method to confirm the leak with the tool, the likely
cause for my symptom, the fix, and how to verify the objects are now
released.