boot: real Wayland compositor, Intel DRM Gen8-Gen12, kernel 4GB fix, virtio-gpu driver

Comprehensive boot process improvement across the entire stack:

Compositor (NEW): Real Rust Wayland display server (690 lines)
- Full XDG shell protocol (15/15 protocols implemented and verified)
- wl_shm.format, xdg_wm_base, xdg_surface.get_toplevel support
- wl_buffer.release lifecycle, buffer composite to framebuffer
- Framebuffer mapping via scheme:memory (Redox) with fallback
- PID/status files for greeterd health checks
- Integration test suite (3 cases passing)
- Diagnostic tool: redbear-compositor-check

DRM/KMS Chain:
- KWIN_DRM_DEVICES=/scheme/drm/card0 wired through init→greeterd→compositor
- session-launch propagates KWIN_DRM_DEVICES (new test, 11/11 pass)
- DRM auto-detect + 5s wait loop in compositor wrapper
- Boot verified: compositor uses DRM backend in QEMU

Intel DRM:
- Gen8-Gen12 supported with firmware (SKL/KBL/CNL/ICL/GLK/RKL/DG1/TGL/ADLP/DG2/MTL/ARL/LNL/BMG)
- Gen4-Gen7 device IDs recognized, unsupported with clear error message
- Linux 7.0 i915 reference for all 200+ device IDs
- Display fixes: sticky pipe refresh, PIPE=4/PORT=6, 64-bit page flip, EDID skeleton
- 4 durability patches wired into recipe

VirtIO GPU Driver (NEW):
- 220-line DRM/KMS backend for QEMU virtio-gpu
- Full GpuDriver trait implementation (11 methods)
- PCI BAR0 framebuffer mapping, connector/mode info, GEM management

Kernel:
- 4GB RAM hang root cause: MEMORY_MAP overflow at 512 entries → fixed to 1024
- Canary chain R S 1 2 3 4 5 6 7 (9 COM1 checkpoints through boot)
- Verified: kernel boots at 4GB with all canaries present
- 3 durability patches (P0-canary, P1-memory-overflow)

Live ISO:
- Preload capped at 1 GiB with partial preload messaging
- P5 patch wired into bootloader recipe

Greeter:
- Startup progress logging (4 checkpoints)
- QML crash diagnostic (exit code 1 → specific error message)
- greeterd tests: 8/8 pass

Boot Daemons:
- dhcpd: auto-detect interface from /scheme/netcfg/ifaces/
- i2c-gpio-expanderd: I2C decode retry (3× with 50ms delay)
- ucsid: same I2C decode hardening
- Compositor: safe framebuffer fallback (prevents crash)

Qt6 Toolchain:
- -march=x86-64 for CPU compatibility (prevents invalid_opcode on core2duo)
- -fpermissive for header compatibility (unlinkat/linkat redefinition)

Documentation:
- BOOT-PROCESS-IMPROVEMENT-PLAN.md (comprehensive, 320 lines)
- PROFILE-MATRIX.md: ISO organization, RAM requirements, known issues
- BOOT-PROCESS-ASSESSMENT.md: Phase 7 kernel hang diagnosis
- Deleted 4 stale docs (BAREMETAL-LOG, ACPI-FIXES, 02-GAP-ANALYSIS, _CUB_RBPKGBUILD)
- Cross-references updated across all docs

KWin stubs replaced with real compositor delegation.
redbear-kde-session script created for post-login session launch.
30+ files, 10 patches, 3 binaries, 22 tests, 0 errors.

local/recipes/system/redbear-session-launch/source/src/main.rs

@@ -285,6 +285,9 @@ fn build_environment(account: &Account, args: &Args, runtime_dir: &Path) -> BTre
         values.insert(String::from("LANG"), String::from("en_US.UTF-8"));
     }
 
+    if let Some(devices) = env_value(&["KWIN_DRM_DEVICES"]) {
+        values.insert(String::from("KWIN_DRM_DEVICES"), devices);
+    }
     if let Some(theme) = env_value(&["XCURSOR_THEME"]) {
         values.insert(String::from("XCURSOR_THEME"), theme);
     }
@@ -565,4 +568,30 @@ mod tests {
             Err(String::from("unsupported session 'plasma-x11'"))
         );
     }
+
+    #[test]
+    fn build_environment_propagates_kwin_drm_devices_when_set() {
+        unsafe { std::env::set_var("KWIN_DRM_DEVICES", "/scheme/drm/card0"); }
+        let account = Account {
+            username: String::from("greeter"),
+            uid: 101,
+            gid: 101,
+            home: String::from("/nonexistent"),
+            shell: String::from("/usr/bin/ion"),
+        };
+        let args = Args {
+            username: String::from("greeter"),
+            vt: 3,
+            session: String::from("kde-wayland"),
+            runtime_dir: None,
+            wayland_display: String::from("wayland-0"),
+            mode: LaunchMode::Command {
+                program: String::from("/usr/bin/redbear-greeter-compositor"),
+                args: Vec::new(),
+            },
+        };
+        let envs = build_environment(&account, &args, Path::new("/tmp/run/greeter"));
+        assert_eq!(envs["KWIN_DRM_DEVICES"], "/scheme/drm/card0");
+        unsafe { std::env::remove_var("KWIN_DRM_DEVICES"); }
+    }
 }