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/unnamed.rs

@@ -0,0 +1,41 @@
+use std::{
+    fs::File,
+    io::{self, prelude::*},
+    os::unix::io::{AsRawFd, FromRawFd, RawFd},
+};
+
+fn from_syscall_error(error: syscall::Error) -> io::Error {
+    io::Error::from_raw_os_error(error.errno as i32)
+}
+fn dup(file: &File, buf: &str) -> io::Result<File> {
+    let stream =
+        syscall::dup(file.as_raw_fd() as usize, buf.as_bytes()).map_err(from_syscall_error)?;
+    Ok(unsafe { File::from_raw_fd(stream as RawFd) })
+}
+
+fn main() -> io::Result<()> {
+    let mut buf = [0; 5];
+    let server = File::create("chan:")?;
+
+    let mut client = dup(&server, "connect")?;
+    let mut stream = dup(&server, "listen")?;
+
+    println!("Testing basic I/O...");
+
+    stream.write(b"abc")?;
+    stream.flush()?;
+    println!("-> Wrote message");
+
+    assert_eq!(client.read(&mut buf)?, 3);
+    assert_eq!(&buf[..3], b"abc");
+    println!("-> Read message");
+
+    println!("Testing connecting to unnamed socket by name (makes no sense)...");
+    assert_eq!(
+        File::open("chan:").unwrap_err().kind(),
+        io::ErrorKind::NotFound
+    );
+
+    println!("Everything tested!");
+    Ok(())
+}