feat: use PDF vector icon for crisp menubar rendering

[jinquan-shi]

• Use PDF icon via systray.SetIcon for sharp 4K display support
• Fall back to PNG template icons if PDF unavailable
• Add thin space between icon and text in tray display
• Add icon_test.go with PDF/PNG validation tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[prakersh]

Thanks for the contribution! The goal of crisp 4K rendering makes sense. A few observations:

Template icon regression

systray.SetIcon(pdfIcon) sets template=false internally, which means the icon won't adapt to macOS light/dark menu bar appearance. The original SetTemplateIcon call sets template=true, which is what makes the icon render correctly in both themes.

PDF format is not cross-platform

The systray library documents supported formats as .ico/.jpg/.png. PDF only works here because the macOS backend calls NSImage initWithData: which happens to support PDF natively - this is an undocumented implementation detail, not a guaranteed API contract. On Linux (D-Bus/StatusNotifierItem) and Windows (HICON), PDF won't work at all.

This is especially relevant since #35 is actively extending the menubar companion to Linux (and Windows is planned after that). Merging a macOS-only icon format now would create an immediate conflict with the cross-platform direction.

Suggestion: use higher-quality PNGs instead

The blurriness on 4K is likely from the source PNGs, not the format itself. A well-crafted PNG exported from the vector source at proper sizes should look crisp on Retina/4K. I'd suggest providing 64x64 or 128x128 hi-res PNGs - SetTemplateIcon will handle the scaling, and it works cross-platform out of the box with no build tags or undocumented behavior needed.

Dead fallback path

Since IconPDF is loaded via go:embed, len(pdfIcon) > 0 will always be true - the PNG fallback branch can never execute.

The thin space and tests are nice additions - happy to keep those parts. Would you be open to swapping the PDF approach for higher-quality PNGs?

[jinquan-shi]

Thanks for the review! @prakersh

Following the feedback regarding 4K rendering and macOS template support, I've updated the PR with the following changes:

1. Reverted PDF to Ultra-High Res PNGs: While the PDF approach aimed for crispness, it was macOS-specific and broke the SetTemplateIcon functionality (causing issues with light/dark mode adaptation). I've replaced the PDF with ultra-high resolution PNGs:

   • icon_template.png: 256x256 (up from 16x16)
   • icon_template@2x.png: 512x512 (up from 32x32)

2. Restored SetTemplateIcon: The code in companion_darwin.go now uses systray.SetTemplateIcon again. This ensures that the icon correctly adapts its color when the user switches between light and dark macOS menu bar themes.

These changes achieve the goal of "crisp 4K rendering" without sacrificing cross-platform compatibility or native macOS behavior.

[prakersh]

Thanks for the updates, @jinquan-shi! The revised approach looks great - ultra-high res PNGs for crisp 4K rendering while keeping SetTemplateIcon for proper light/dark mode adaptation. Clean and well-tested. Merging!