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/scheme-utils/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "scheme-utils"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
+libredox.workspace = true
+redox-scheme.workspace = true
+redox_syscall.workspace = true
+
+[lints]
+workspace = true