[leak-fix] Fix ListView.RefreshCommand memory leak (Fixes #36539)

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🤖 AI-generated PR — produced automatically by the Memory Leak Fixer agentic workflow from issue #36539. The regression test below was observed to FAIL on unpatched main and PASS with this fix, on the runner. Please review carefully before merging.

Fixes #36539
Refs: #36539
Target branch: main
Attempt: 2/3

The leak

ListView.RefreshCommand subscribes to the command's CanExecuteChanged event (src/Controls/src/Core/ListView/ListView.cs, OnRefreshCommandChanged). The subscription was a plain newCommand.CanExecuteChanged += OnCommandCanExecuteChanged and was only removed when the command was reassigned — never on unload. When the command's CanExecuteChanged is a plain CLR event (as is common for custom/ViewModel ICommand implementations), the delegate target is the ListView, so a shared/long-lived command strongly roots the ListView (and its page). MAUI's own Command raises CanExecuteChanged through a WeakEventManager and would not leak, but arbitrary ICommand implementations do.

The fix

Replace the plain subscription with the existing idiomatic WeakCommandSubscription (the same helper Button/CommandElement already use). It links the ListView to the handler via a DependentHandle so the command holds the ListView only weakly, and disposes the previous subscription when the command is replaced. No behavior change to RefreshAllowed/CanExecute evaluation.

Regression test

ListViewMemoryLeakTests.ListViewDoesNotLeakWhenRefreshCommandIsLongLived in src/Controls/tests/Core.UnitTests/ListViewMemoryLeakTests.cs. It assigns a long-lived ICommand (with a plain CanExecuteChanged event) to RefreshCommand, drops the ListView, forces GC, and asserts the ListView is collected.

State	Result
Without fix (unpatched main)	❌ test FAILS (control retained)
With fix	✅ test PASSES (control collected)

Without fix: Failed ListViewDoesNotLeakWhenRefreshCommandIsLongLived [814 ms]
  ListView should not be alive! It is being rooted by the RefreshCommand's CanExecuteChanged subscription.
With fix:    Passed ListViewDoesNotLeakWhenRefreshCommandIsLongLived [54 ms]

All 71 neighbouring ListViewTests still pass.

Scope

Managed cross-platform change (src/Controls/src/Core/ListView/ListView.cs) → all platforms. No public API change.

Generated by Memory Leak Fixer · 280.8 AIC · ⌖ 29.8 AIC · ⊞ 19.7K · ◷

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