Implement Debug manually for PipeSecurityAttributes on Windows

The windows_sys::Win32::Security::SECURITY_ATTRIBUTES struct is a raw C FFI
struct that does not implement std::fmt::Debug. Deriving Debug on
PipeSecurityAttributes failed Windows compilation with E0277.

Key changes:
- In crates/tsunagi/src/ipc/windows.rs, remove #[derive(Debug)] on
  PipeSecurityAttributes and provide an explicit std::fmt::Debug
  implementation formatting nLength, lpSecurityDescriptor, and
  bInheritHandle.

Validation on Linux:
- Verified type check against Windows target via rustc.
- cargo fmt --all -- --check passed.
- cargo clippy --locked --workspace --all-targets -- -D warnings passed.
- cargo test --locked --workspace --all-targets --jobs 2 -- --test-threads=2 passed (349 tests passed).

crates/tsunagi/src/ipc/windows.rs

@@ -61,11 +61,20 @@ const ERROR_PIPE_BUSY: i32 = 231;
 /// - `S:(ML;;NW;;;ME)`: SACL Mandatory Label with Medium Integrity (`ME`) and No Write Up (`NW`).
 ///   This allows unprivileged user-space processes (Medium Integrity) to write to the
 ///   named pipe even when the agent runs as an elevated Administrator (High Integrity).
-#[derive(Debug)]
 struct PipeSecurityAttributes {
     attrs: windows_sys::Win32::Security::SECURITY_ATTRIBUTES,
 }
 
+impl std::fmt::Debug for PipeSecurityAttributes {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("PipeSecurityAttributes")
+            .field("nLength", &self.attrs.nLength)
+            .field("lpSecurityDescriptor", &self.attrs.lpSecurityDescriptor)
+            .field("bInheritHandle", &self.attrs.bInheritHandle)
+            .finish()
+    }
+}
+
 impl PipeSecurityAttributes {
     fn new() -> Result<Self> {
         use std::ffi::OsStr;