Add desktop app service and VM dev session tooling

Introduces a new `core/applications` QML/C++ module (`Nebula.Applications`) to discover `.desktop` entries, expose filterable application models, and launch installed apps safely from the shell. The desktop launcher now uses real installed apps with themed icon loading and fallback glyphs, adds output-aware surface sizing via `OutputTracker`, and wires in image/icon providers. It also adds VMware-focused Sway/shell wrapper scripts, updates Sway config/session env defaults, and refreshes README docs to document the new development flow and Desktop 0.1 behavior.

compositor/README.md

@@ -7,7 +7,7 @@ Sway currently provides:
 - Wayland compositor
 - application window management
 - XWayland
-- input
+- input and the pointer cursor
 - output handling
 
 Nebula provides the visible shell (Qt Quick/QML via LayerShellQt). The Sway config must not enable a Sway bar.
@@ -25,3 +25,61 @@ Nebula compositor    later
 Nebula Shell
 Qt Quick/QML
 ```
+
+## Development session
+
+From the NebulaOS repository root:
+
+```bash
+sway -c compositor/sway/nebula-sway.conf
+```
+
+Recommended on the Ubuntu VMware VM (repo-root `cd`, cursor environment, software cursors):
+
+```bash
+./compositor/sway/dev/run-sway-vm.sh
+```
+
+Sway then autostarts Nebula Desktop through `scripts/run-nebula-vm.sh`.
+
+Skip shell autostart:
+
+```bash
+NEBULA_SHELL_AUTOSTART=0 ./compositor/sway/dev/run-sway-vm.sh
+```
+
+### Output / resolution
+
+The development config uses scale `1` and requests `1920x1080` when that mode is advertised. If it is not, Sway keeps the preferred mode. This is a VM convenience, not a production requirement.
+
+```bash
+swaymsg -t get_outputs
+swaymsg output <name> mode 1920x1080
+swaymsg output <name> scale 1
+```
+
+### Cursor
+
+```text
+seat * xcursor_theme Adwaita 24
+XCURSOR_THEME=Adwaita
+XCURSOR_SIZE=24
+```
+
+Requires `adwaita-icon-theme`. A Nebula-branded cursor theme is a later task.
+
+`WLR_NO_HARDWARE_CURSORS=1` is VMware-specific and is set by `run-sway-vm.sh`, not by production session files.
+
+### Emergency shortcuts
+
+| Shortcut | Action |
+|----------|--------|
+| Super+Enter | open Foot |
+| Super+Shift+E | exit Sway |
+| Super+Shift+C | reload Sway config |
+
+Normal application launching is done from the Nebula launcher, not these shortcuts.
+
+### Rendering
+
+`scripts/run-nebula-vm.sh` sets `QT_QUICK_BACKEND=software` for the VMware guest GPU. Production `nebula-shell` must not set that variable.