fix(linux): niri hint offset via show-geometries

[ivelieu]

this uses the niri msg -j show-geometries command provided by niri-wm/niri#3305.

Description

as discussed on the discord, this is blocked on niri merging a method to query precise window offsets.

Initially I tried doing this implementation with niri-wm/niri#4147, but I realised only after doing it that the data it provides alone is insufficient to get the offsets from waybar/dms/noctalia and niri's horizontal padding. Using niri-wm/niri#3305 is much simpler.

I don't expect this to get merged until upstream does, for now this is just for others that may want a fix in the meantime like me.

Target Platform

• Platform-agnostic (shared logic, no OS-specific code)
• macOS
• Linux
• Windows

Type of Change

• feat — New feature
• fix — Bug fix
• refactor — Code restructuring (no behavior change)
• perf — Performance improvement
• docs — Documentation only
• test — Adding or updating tests
• chore — Build, CI, dependencies, tooling

Cross-Platform Checklist

• OS-specific files use correct build tags (e.g., //go:build darwin)
• No darwin imports from untagged (shared) code — The One Rule
• Stub implementations added for other platforms (returning CodeNotSupported)
• N/A — This PR does not touch platform-specific code

General Checklist

• Code formatted (just fmt)
• Linters pass (just lint)
• Tests pass (just test)
• Build succeeds (just build)
• Tests added/updated for new or changed functionality
• Documentation updated (if applicable)
• Commit messages follow conventional commits

Screenshots / Recordings

neruhintlabels.mp4

[y3owk1n]

Amazing work! i have added a pending upstream label for this. We can wait 😉