feat(slash-worker): self-terminate on parent death via create_time watchdog

Daemon thread polls _is_orphaned (original ppid check + psutil create_time PID-reuse
guard, no PR_SET_PDEATHSIG). On orphan, drains an in-flight command up to a grace
window then os._exit(0). Started before the HermesCLI build to cover the spawn window.

Task: swl-qrf.8

tests/test_slash_worker_watchdog.py

@@ -0,0 +1,21 @@
+import psutil
+
+from tui_gateway import slash_worker
+
+
+def test_is_orphaned_true_when_ppid_changes():
+    # Our parent went away and we were reparented to a subreaper/init.
+    assert slash_worker._is_orphaned(1234, 1.0, getppid=lambda: 999999) is True
+
+
+def test_is_orphaned_true_when_parent_create_time_mismatch():
+    # Same ppid but a different create_time means the PID was reused.
+    me = psutil.Process()
+    assert slash_worker._is_orphaned(me.pid, 0.0, getppid=lambda: me.pid) is True
+
+
+def test_is_orphaned_false_when_parent_alive_and_matches():
+    me = psutil.Process()
+    assert (
+        slash_worker._is_orphaned(me.pid, me.create_time(), getppid=lambda: me.pid) is False
+    )