Updates UI theme metrics for traffic-light controls and chrome inset to slightly larger values. In the desktop window chrome surface, positioning now uses the title bar center directly, rounds rendered margins, and introduces short easing animations for X/Y chrome offsets to reduce jitter during movement.
Adds focused title-bar geometry to the window service and updates the Sway backend to derive frame data more reliably (including parent node fallback and content rect tracking for wrapped/floating views). Window chrome positioning now centers against the actual title bar instead of deco offsets, improving alignment. Also refreshes visual sizing/padding for traffic-light controls and Sway titlebar spacing to match the new chrome metrics.
Introduces a dedicated layer-shell `WindowChromeSurface` that renders macOS-style traffic-light controls over the focused Sway window titlebar, replacing the old top-bar window controls. Adds theme tokens and a reusable `TrafficLightButton` component, updates shell QML/CMake wiring, and adjusts Sway titlebar padding/title format so window titles do not overlap the overlay. Window tracking was extended with focused-window geometry/deco/fullscreen properties plus backend refresh support so the chrome follows window movement and state changes in near real time.
Introduces a new `WindowControls` component in the desktop top bar with minimize, maximize/restore, and close actions for the focused window. `WindowService` now exposes focused-window presence/maximized state plus focused-window convenience actions to support this UI.
Also extends Nebula UI with a reusable `NebulaToolTip`, keyboard/pressed-state support in `NebulaIconButton`, new window-control glyphs in `NebulaIcon`, and theme tokens for pressed/danger hover states, with CMake and README updates to register/document the new components.
Introduce a new production desktop shell at `shells/desktop/shell` built with C++20, Qt Quick/QML, and LayerShellQt, including top bar, launcher, desktop surfaces, shell state, and mock app data. Add the shared `packages/nebula-ui` QML module (theme, controls, focus, icons) and wire it into the shell build.
Retire the old GTK/WebKit native host by removing `shells/desktop/native`, move the React shell UI to `shells/desktop/prototype-react` as an archived design reference, and update root/compositor/session documentation to reflect the new Linux-only production architecture and temporary Sway role.
andrew