feat: add match.is_alone window rule

[Yocraft-2000]

Summary

Added is_alone window rule match.
Floating windows are ignored, the rule only match tiled windows.
Revert only if toggle by the rule, a window opened fullscreen will not unfullscreen when opening another one.
Re-evaluated whenever the tiled windows change (open, close, move, float toggle, etc) and on config reload.

Motivation

Objective is to find an optimal solution to #93, #177 and also the already added expand_single_column.
One window rule that can do all of that is better than a lot of random options.

This one resolve #93 :

[[window_rule]]
match.is_alone = true
default_maximize_to_edges = true

This one resolve #177 :

[[window_rule]]
match.is_alone = true
default_width = 0.75

this one replace expand_single_column :

[[window_rule]]
match.is_alone = true
default_maximize = true

It can also extend to a lot of other use cases.

Type of Change

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

Related Issue

Closes #93 and #177.
Related to the already merged #48.

Testing

just format
just test
just lint

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

[ItsLemmy]

Thanks!