Summary

Fixes an InvalidCastException at runtime under XAML parsing whenever a control with a Command binding gets templated. Root cause: upstream PR dotnet#10715 (cherry-picked here as 87befda) inlined a typeof() call with the wrong class, so two sibling `WeakEventManager` subclasses now register at the same dictionary key. Whichever wins the race makes the other one's cast throw.

Also adds a `commit_denylist` mechanism so the same upstream commit cannot be re-applied accidentally.

The bug

In `CommandManager.cs`:

```csharp
// Before (correct):
Type managerType = typeof(RequerySuggestedEventManager);
RequerySuggestedEventManager manager = (RequerySuggestedEventManager)GetCurrentManager(managerType);
...
SetCurrentManager(managerType, manager);

// After upstream PR dotnet#10715 (broken):
RequerySuggestedEventManager manager = (RequerySuggestedEventManager)GetCurrentManager(typeof(CanExecuteChangedEventManager));
...
SetCurrentManager(typeof(CanExecuteChangedEventManager), manager);
```

`CanExecuteChangedEventManager` is a public class in the same file pair; it already used `typeof(CanExecuteChangedEventManager)` for its own key. After PR dotnet#10715, both managers register at `typeof(CanExecuteChangedEventManager)`. Whichever is constructed first wins; the loser's `CurrentManager` getter retrieves the wrong instance and the cast throws `InvalidCastException: Unable to cast object of type 'CanExecuteChangedEventManager' to type 'RequerySuggestedEventManager'`.

Repro stack trace (real):
```
at System.Windows.Input.CommandManager.RequerySuggestedEventManager.get_CurrentManager()
at System.Windows.Input.CommandManager.add_RequerySuggested(EventHandler)
at WpfFramework.VM.DelegateCommand.add_CanExecuteChanged(EventHandler)
at System.Windows.Input.CanExecuteChangedEventManager.HandlerSink..ctor(...)
at System.Windows.Input.CanExecuteChangedEventManager.AddHandler(...)
at System.Windows.Controls.Primitives.ButtonBase.HookCommand(ICommand)
at System.Windows.Controls.Primitives.ButtonBase.OnCommandChanged(...)
```

The bug was latent on JIT-only builds (the SO discussed in #1 happened first) but became reproducible on R2R'd builds where the static-init order pinned `CanExecuteChangedEventManager` as the first registrant.

What changed

`src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Command/CommandManager.cs` — restore the key to `typeof(RequerySuggestedEventManager)` (its own type) on both `Get` and `Set` calls. Inline form preserved (no need to reintroduce the `managerType` local; that style choice is a separate concern).

`CanExecuteChangedEventManager.cs` is intentionally left unchanged. Its own keys were always `typeof(CanExecuteChangedEventManager)` and that's still the correct identity for it.

commit_denylist mechanism

To prevent this commit from being re-cherry-picked (the cherry-pick automation pulls h3xds1nz PRs in batches):

• `.if-fork/config.yaml` — new `commit_denylist` section, with upstream commit `0e965e795...` entered as the first denied entry (PR ref + reason).
• `tools/config-schema.json` — schema for the new section.
• `tools/check-commit-denylist.py` — hard-gate checker. Walks `(cherry picked from commit ...)` trailers up the chain, so a re-pick of any descendant of a denied commit is also refused. Returns exit 2 + JSON verdict.
• `.if-fork/prompts/cherry-pick.md` — new Step 2.5 calls the checker before the graduation check; on match, emits a ledger event `refused` with reason `commit_denylist` and exits.

Verification

• crossgen2-compiled InitialForce.WPF if.63 nupkg consumed by MotionCatalyst → reproduces the cast failure during MainWindow template loading.
• After this fix (built locally → if.64), the same app starts cleanly past the templating phase.
• `python tools/check-commit-denylist.py 87befda` → exit 2, verdict `denied`, matched via the upstream SHA in the trailer.
• Test runs unmodified; no behavior change to `CanExecuteChangedEventManager` paths.

Upstream

Comment will be filed on dotnet#10715 with a sanitized repro so upstream can fix in their tree before this commit propagates further.

🤖 Generated with Claude Code