Adds a runtime-detected "Klassy (auto-detect)" preset for the custom
window controls that reads the user's Plasma decoration theme and
applies matching colors and shape. When Klassy itself is not installed
but Plasma is, the option re-labels to "Plasma (auto-detect)" and
still applies the desktop color scheme. Hidden on non-KDE / non-Linux.
Backend:
* New desktop_theme module parses kwinrc, kdeglobals, and klassyrc
without external deps. Exposes detect_desktop_theme Tauri command
returning DesktopThemeInfo: desktop id, isKlassy flag, WM active/
inactive background + foreground, accent, DecorationHover, and the
user's Klassy ButtonIconStyle / ButtonShape when present.
Frontend:
* windowControlsStore gains applyKlassyPreset(), a cached detection
helper, and mapKlassyShapeToQbz() that maps Klassy's button shapes
(FullHeightRectangle, FullHeightRoundedRectangle, Tab, Circle,
Square, IntegratedRoundedRectangle, ...) onto QBZ's shape set.
* Adds the full-height-rounded shape to ButtonShape to cover the
most common Klassy style that QBZ was missing; CSS matches Klassy
FullHeightRoundedRectangle visual (full-height tab with ~7px
radius and margin).
* SettingsView fires detection on mount, derives the preset list
reactively so the auto-detect option only appears when relevant,
and adds the new shape to the Style picker.
* i18n keys added for the new shape and both preset labels in en/es.
cc
vicrodh
6a5cfc7235