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/helloserver.rs

@@ -0,0 +1,21 @@
+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 main() -> io::Result<()> {
+    let server = File::create("chan:hello")?;
+
+    loop {
+        let stream =
+            syscall::dup(server.as_raw_fd() as usize, b"listen").map_err(from_syscall_error)?;
+        let mut stream = unsafe { File::from_raw_fd(stream as RawFd) };
+
+        stream.write(b"Hello World!\n")?;
+    }
+}