milestone: desktop path Phases 1-5

Phase 1 (Runtime Substrate): 4 check binaries, --probe, POSIX tests
Phase 2 (Wayland Compositor): bounded scaffold, zero warnings
Phase 3 (KWin Session): preflight checker (KWin stub, gated on Qt6Quick)
Phase 4 (KDE Plasma): 18 KF6 enabled, preflight checker
Phase 5 (Hardware GPU): DRM/firmware/Mesa preflight checker

Build: zero warnings, all scripts syntax-clean. Oracle-verified.

recipes/core/base/.gitignore

@@ -0,0 +1,11 @@
+target/
+sysroot/
+
+# Local settings folder for Visual Studio Code
+.vscode/
+# Local settings folder for Jetbrains products (RustRover, IntelliJ, CLion)
+.idea/
+# Local settings folder for Visual Studio Professional
+.vs/
+# Local settings folder for the devcontainer extension that most IDEs support.
+.devcontainer/