Add an executable picker to the Windows launcher

[maoyouaa]

Summary

• Open a native executable picker when zluda.exe is launched without arguments.
• Exit cleanly when the picker is cancelled.
• Preserve existing command-line and drag-and-drop usage.
• Correctly quote Windows child-process arguments, including paths with spaces, quotes, and trailing backslashes.

Testing

• Added regression tests for Windows command-line serialization.
• Verified x64 and i686 Windows builds.
• Built and packaged the complete Debug runtime.
• Verified picker selection and cancellation manually.
• Launched C:\Program Files\dotnet\dotnet.exe --version from the packaged build with exit code 0.

Closes #653