Fullscreen titlebar follows OS theme instead of app theme (macOS 26 fullscreen chrome)

[pHequals7]

Summary

When the dashboard is in fullscreen and the app is set to the light theme (while the OS is dark), the titlebar strip renders dark (#212628 measured) instead of following the app theme. Windowed mode is fixed by #433; fullscreen is not.

Evidence (measured on macOS 26, MuesliDevA)

• Pixel samples of the fullscreen titlebar strip: #212628 across the full width, with traffic lights (green #00BD36) on it — the system's dark-vibrant fullscreen chrome material.
• Setting window.appearance (the Fix dark titlebar when the app is set to the light theme #433 approach) fixes windowed chrome only.
• Setting NSApp.appearance (added in 355a485) aligns menus/panels but does not affect the fullscreen strip.
• Spike: adding .fullSizeContentView extends app content behind the traffic lights (sidebar renders white under them — looks like a forced overlay) while the strip to the right still renders dark. Reverted; it trades one visual bug for a worse one without fixing the strip.

Analysis

On macOS 26 the fullscreen titlebar is drawn by auxiliary system chrome that resolves against the OS appearance, not the app's window or NSApp appearance. With the current style mask (titlebarAppearsTransparent without .fullSizeContentView) it renders as an opaque dark strip.

Options

1. Accept as OS-governed behavior (Safari and most apps behave the same in fullscreen).
2. Rework the window chrome (e.g. .fullSizeContentView with proper content insets, or hiding the titlebar in fullscreen) — needs a dedicated design pass so traffic lights and content don't fight, with before/after pixel verification.

References

• Fix dark titlebar when the app is set to the light theme #433 (windowed chrome fix, merged scope)
• 355a485 (NSApp-level appearance sync + toggle hit area)

[pHequals7]

Update: fixed by #434's opaque titlebar. The earlier analysis held only for the transparent-titlebar configuration — with titlebarAppearsTransparent = false, the fullscreen titlebar resolves against the window's own appearance (synced to the app theme by the #433 machinery), including in fullscreen.

Verified by pixel sampling on a dev build (OS dark + app light, fullscreen): the strip reads #FFFFFF (was #212628 before the fix), content #F0F0F2. Dark theme renders consistently dark in fullscreen as well.

Closing once #434 merges.

[pHequals7]

Fixed by #434 (merge commit f44b238): the opaque titlebar resolves against the window's synced appearance in both windowed and fullscreen modes. Pixel-verified: fullscreen strip #FFFFFF in light theme with OS dark.