fix: generate AppKit BindCommand bindings that compile against ObjCRuntime.Selector

[glennawatson]

Summary

A generated BindCommand to an AppKit control now compiles on macOS.

• The AppKit command binding no longer disposes its selector. The generated code assigns new ObjCRuntime.Selector("theAction:") to the control's Action and clears it on detach. It no longer calls Dispose(), which ObjCRuntime.Selector does not have.

Why

Binding a command to an NSButton, or any other AppKit target/action control, failed to compile with CS1061.

• The generated detach code called Dispose() on an ObjCRuntime.Selector. That type has no Dispose in any macOS reference assembly from net8.0 to net11.0.
• The macOS example in docs: examples for the remaining public API, including Apple platforms ReactiveUI#4526 falls back to BindCommandUnsafe because of this. Once a release carries this fix, it can use BindCommand.

Breaking changes

None.

How this was verified

The native command tests now use a Selector stand-in with the real type's shape, so the old call no longer compiles.

• By hand: ran the generator on the example's NSButton BindCommand call and compiled the output against the real Microsoft.macOS.dll reference assembly with no errors. No Apple host was available to run it.

Notes for the reviewer

The whole change is AppKitCommandEmitter.

• The test fixture change only removes IDisposable from the fake ObjCRuntime.Selector.

Checklist

• I have read the Contribute guide
• The PR title follows Conventional Commits
• Tests cover this change, or the summary says why they do not
• New or changed public API has XML documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.20%. Comparing base (938828f) to head (0f95499).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #150   +/-   ##
=======================================
  Coverage   99.20%   99.20%           
=======================================
  Files         385      385           
  Lines       14265    14263    -2     
  Branches     2018     2018           
=======================================
- Hits        14151    14150    -1     
+ Misses        114      113    -1     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud