Fix SAS Service build errors

- Use raw FFI for named pipe operations instead of windows crate APIs
- Add Win32_System_IO feature to Cargo.toml
- Define pipe constants manually to avoid missing exports

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

agent/Cargo.toml

@@ -77,6 +77,7 @@ windows = { version = "0.58", features = [
     "Win32_Storage_FileSystem",
     "Win32_System_Pipes",
     "Win32_System_SystemServices",
+    "Win32_System_IO",
 ]}
 
 # Windows service support