fix: honor deactivated unfullscreen when activation follows

[Yocraft-2000]

Summary

honor deactivated unfullscreen when activation follows

English isn't my native language so I asked AI to summarize the changes to make them clearer:

A client that sheds fullscreen while deactivated had its request denied
to protect Wine-style minimize-on-focus-loss games. That broke opening a
url into a fullscreen video player from another workspace: firefox ends
its video fullscreen and requests unfullscreen before its xdg-activation
lands, so the request was dropped and the configure re-asserted
fullscreen, leaving a black screen until a manual toggle.

Park such requests instead of denying them: an xdg or foreign activation
focusing the view within 750ms applies the parked request, anything else
lets it expire silently. Any honored or manual state change supersedes
a parked request.

Motivation

When I have youtube in fullscreen for example and I open a tab with firefox <url> from another workspace, firefox shows a black screen until I manually exit fullscreen. It doesn't exit fullscreen automatically.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Build / packaging
• Documentation

Related Issue

Testing

Opening a new tab from another workspace with xdg or firefox leaves fullscreen. I can't test wine games since I don't have any.

Manual Coverage

• Tested in a nested Umbriel session
• Tested in a native Umbriel session
• Tested with multiple monitors
• Tested with a scaled output
• Tested with native Wayland applications
• Tested with X11 applications through xwayland-satellite
• Tested with the scrolling layout
• Tested with the dwindle layout

Screenshots / Videos

Checklist

• This PR is ready for review, or it is marked as Draft.
• I read and followed the relevant guidance in CONTRIBUTING.md.
• I initialized and updated the SceneFX submodule where required.
• I ran just format, or this PR has no C++ changes.
• I ran the relevant build, test, lint, or verification commands, or explained why they were not run.
• I functionally verified compositor behavior where automated checks are insufficient.
• I self-reviewed the changes.
• I checked for new warnings or errors.
• I updated docs/ and examples/config.toml, or this PR does not change user-facing configuration or behavior.
• I used canonical names for config keys, IPC actions, paths, and identifiers.

Additional Notes

I didn't update the comments in the code.