Feature: HiDPI scaling, accessibility and toolbar labels on Linux

[MemerGamer]

What

• HiDPI: Uno X11 takes the scale from UNO_DISPLAY_SCALE_OVERRIDE, else Xft.dpi (set by KDE/GNOME on X11). New DisplayScaleResolver falls back to QT_SCALE_FACTOR, QT_SCREEN_SCALE_FACTORS, GDK_SCALE when Xft.dpi is absent (XWayland). Default window size cap (1600x1000) is now logical, not physical, so it no longer shrinks at 2x. Checked headless at 1.25, 1.5 and 2.0: icons are requested at physical size (already the case), CSD buttons and 1px borders are crisp. headless-run.sh gains FILES_HEADLESS_XFT_DPI.
• Translations: non-en-US locales fall back to en-US (verified with LANG=de_DE: untranslated "Open in terminal" shows English). Removed 7 empty translations (fil-PH, hi-IN, id-ID) that would have shown blank labels. Added missing en-US keys that code referenced (Error, FolderItemAutomation, CommitsNumber, SettingsAboutAppName, StatusCenter_PrepareInProgress). New tests (ResourceKeyTests) fail if code or XAML references a key missing from en-US, or a locale defines an empty value.
• Accessibility: localized names for the sidebar toggle, "see more" and status-center chevron buttons. Toolbar focus rectangle is no longer clipped.
• Polish: Sort and Layout toolbar buttons show labels (Win11 Explorer style); Settings > Appearance > Toolbar has a switch to go back to icon-only (ShowToolbarSortViewLabels, default on).

Not done / known issues

• Menu drop shadows skipped (kept the 1px border).
• Light theme: moving keyboard focus onto the toolbar buttons (Group, Sort, Layout, preview pane) leaves them rendered faded/white until restyled; dark theme is fine and mouse hover is fine. Cause not found (likely theme-resource resolution in the AppBarButton template).

🤖 Generated with Claude Code

https://claude.ai/code/session_01LeKXJc3DnK3PzAqwgA72NY