Add tray desktop notification helper

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

enodia_sentinel/tray/notify.py

@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+"""Desktop notification helper. Prefers notify-send; no GUI imports."""
+from __future__ import annotations
+
+import shutil
+import subprocess
+from typing import Callable, Optional, Sequence
+
+Runner = Callable[[Sequence[str]], "subprocess.CompletedProcess"]
+
+
+def _default_runner(cmd: Sequence[str]) -> "subprocess.CompletedProcess":
+    try:
+        return subprocess.run(list(cmd), capture_output=True, text=True,
+                              timeout=10, check=False)
+    except (OSError, subprocess.TimeoutExpired) as exc:
+        return subprocess.CompletedProcess(list(cmd), 127, "", str(exc))
+
+
+def notify(title: str, body: str, *, runner: Optional[Runner] = None,
+           which: Callable[[str], object] = shutil.which) -> bool:
+    """Show a desktop notification. Returns True if notify-send was invoked."""
+    if which("notify-send") is None:
+        return False
+    run = runner or _default_runner
+    run(["notify-send", "-a", "Enodia Sentinel", title, body])
+    return True