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.

session/nebula-session

@@ -1,11 +1,20 @@
 #!/bin/sh
-# NebulaOS session startup
+# NebulaOS production session startup
+#
+# Production must start nebula-shell without QT_QUICK_BACKEND=software.
+# GPU-accelerated Qt Quick is the production default.
+#
+# The Ubuntu VMware development VM is different: use
+# compositor/sway/dev/run-sway-vm.sh (or sway -c compositor/sway/nebula-sway.conf
+# from the repository root) so the development wrapper can set the software
+# scene-graph backend.
 
 set -e
 
 export XDG_CURRENT_DESKTOP=NebulaOS
 export XDG_SESSION_DESKTOP=nebula
+export XCURSOR_THEME="${XCURSOR_THEME:-Adwaita}"
+export XCURSOR_SIZE="${XCURSOR_SIZE:-24}"
 
-# Shell and services are wired here as they land
 # Production desktop chrome: shells/desktop/shell (nebula-shell)
 # exec nebula-shell