fix: apply is_alone window rule before the window opens, prevent flashing at default width

[Yocraft-2000]

Summary

A window that opens as the sole tiled window on its workspace is now configured from the first configure and at attach in its match.is_alone rule state (width, fullscreen, maximize).
That state is owned by the alone rule, so it reverts as soon as a second window opens, without ever taking over a state the client itself requested (e.g. mpv opening fullscreen on its own).

Motivation

The window flash at default width before applying the rule.

Type of Change

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

Related Issue

Testing

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.
• This change fits SCOPE.md, or its scope was agreed in an issue or on Discord first.
• I read and followed the relevant guidance in CONTRIBUTING.md.
• 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

[Noctalia-CI]

The description now contains the required template structure.

[ItsLemmy]

Thanks!