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.

local/patches/base/P0-workspace-add-bootstrap.patch

@@ -0,0 +1,12 @@
+diff --git a/Cargo.toml b/Cargo.toml
+index 9e776232..acdb1c97 100644
+--- a/Cargo.toml
++++ b/Cargo.toml
+@@ -2,6 +2,7 @@
+ resolver = "2"
+ members = [
+     "audiod",
++    "bootstrap",
+     "config",
+     "daemon",
+     "dhcpd",