fix(view): uniform rounding rule for main surface and subsurfaces

[nikoloc]

Summary

unified the logic for main surface rounding to match the one used for subsurfaces. main surface should not be rounded unconditionally, since its position in the windows coordinate space may not be at the start, observed in the fastpotify client

Motivation

solves the problem described above

Type of Change

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

Related Issue

Testing

manually tested with mentioned client, and some other apps, both with and without csd. seems like there are no regressions. did not run the automated tests.

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

[nikoloc]

the sharp edge that can be seen in both screenshots seems to be another issue. i dont have an idea why is happens, but i have seen it in other places