test(maestro): skip sidecar-rollback test under root (pre-existing CI red)

CI runs as root, where the 0o500 read-only sidecar dir doesn't block the
write the test relies on failing — so it reported a spurious failure and
has reddened main since commit 149. Probe writability and skip when root;
non-root runs still assert the rollback.

crates/maestro-daemon/tests/session_manager.rs

@@ -84,6 +84,19 @@ async fn create_rolls_back_tmux_session_when_sidecar_write_fails() {
     std::fs::create_dir_all(&sidecar_dir).unwrap();
     std::fs::set_permissions(&sidecar_dir, std::fs::Permissions::from_mode(0o500)).unwrap();
 
+    // The failure is injected by making the sidecar dir read-only — but root
+    // bypasses directory permission bits, so the write would succeed and the
+    // rollback path never trigger. CI runs as root; detect that with a write
+    // probe and skip rather than report a spurious failure (the rollback is
+    // still covered in any non-root environment).
+    let probe = sidecar_dir.join(".perm_probe");
+    if std::fs::write(&probe, b"x").is_ok() {
+        let _ = std::fs::remove_file(&probe);
+        std::fs::set_permissions(&sidecar_dir, std::fs::Permissions::from_mode(0o700)).unwrap();
+        eprintln!("skipping: sidecar dir writable despite 0o500 (running as root?)");
+        return;
+    }
+
     let res = fx
         .manager
         .create(CreateSessionRequest {