Add Nebula.Windows with Sway IPC backend

Introduces a new `core/windows` module (`Nebula.Windows`) with `WindowService`, window/workspace models, and a Sway IPC backend for live window tracking and control (focus, close, move/resize, snap, maximize/restore, minimize, workspace switch). The desktop shell now links this module, uses compositor focus for top-bar active app text, and adds an Open Windows section in the launcher with focus/close actions.

Also updates application metadata handling to parse `StartupWMClass` and map window `app_id`/class to friendly names and icons, and revises Sway config/docs for the new floating-first Desktop 0.2 behavior with temporary compositor-provided decorations.

core/applications/README.md

@@ -2,13 +2,14 @@
 
 Shared C++ service for discovering and launching installed Linux applications from `.desktop` entries.
 
-Desktop and the future Bigscreen shell should both use this library. It has no Desktop-specific QML.
+Desktop and the future Bigscreen shell should both use this library. It has no Desktop-specific QML. Window naming helpers (`displayNameForWindow`, `iconNameForWindow`) are intended for `WindowService`.
 
 ## Behaviour
 
 - Scans XDG application directories (`XDG_DATA_HOME`, `XDG_DATA_DIRS`, with the usual `~/.local/share` and `/usr/share` defaults).
 - Hides entries with `Hidden=true` or `NoDisplay=true`, and respects `OnlyShowIn` / `NotShowIn` / `TryExec`.
 - Exposes a `QAbstractListModel` to QML (`desktopId`, `name`, `genericName`, `comment`, `iconName`, `categories`, `terminal`).
+- Parses `StartupWMClass` and can map a compositor `app_id` / window class to a friendly `Name` (`displayNameForWindow`, `iconNameForWindow`) for `WindowService`.
 - Launches with `QProcess::startDetached` and `QProcess::splitCommand`. Does not use a shell.
 - Strips or substitutes common Exec field codes when launching without files/URLs.