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/ipcd/examples/shm.rs

@@ -0,0 +1,56 @@
+use std::{fs::File, io, os::unix::io::AsRawFd, slice};
+
+fn from_syscall_error(error: syscall::Error) -> io::Error {
+    io::Error::from_raw_os_error(error.errno as i32)
+}
+fn main() -> Result<(), io::Error> {
+    let file1 = File::open("shm:example")?;
+    let file2 = File::open("shm:example")?;
+
+    let one = unsafe {
+        slice::from_raw_parts_mut(
+            syscall::fmap(
+                file1.as_raw_fd() as usize,
+                &syscall::Map {
+                    offset: 0,
+                    size: 128,
+                    flags: syscall::PROT_READ | syscall::PROT_WRITE | syscall::MAP_SHARED,
+                    address: 0,
+                },
+            )
+            .map_err(from_syscall_error)? as *mut u8,
+            128,
+        )
+    };
+    // FIXME: While the length can be unaligned, the offset cannot. This test is incorrectly
+    // written.
+    let two = unsafe {
+        slice::from_raw_parts_mut(
+            syscall::fmap(
+                file2.as_raw_fd() as usize,
+                &syscall::Map {
+                    offset: 64,
+                    size: 64,
+                    flags: syscall::PROT_READ | syscall::PROT_WRITE | syscall::MAP_SHARED,
+                    address: 0,
+                },
+            )
+            .map_err(from_syscall_error)? as *mut u8,
+            64,
+        )
+    };
+
+    println!("Testing writing between");
+    for i in 0..128 {
+        one[i as usize] = i;
+    }
+    for i in 0..64 {
+        assert_eq!(two[i as usize], 64 + i);
+    }
+
+    println!("Testing fpath");
+    let mut buf = [0; 128];
+    let len = syscall::fpath(file1.as_raw_fd() as usize, &mut buf).map_err(from_syscall_error)?;
+    assert_eq!(&buf[..len], b"shm:example");
+    Ok(())
+}