diag: log all hermes processes on unexpected gateway shutdown (#9905)

When the gateway receives SIGTERM/SIGINT, the shutdown handler now
runs 'ps aux' and logs every hermes/gateway-related process (excluding
itself). This will show in agent.log as:

  WARNING: Shutdown diagnostic — other hermes processes running:
    hermes  1234 ... hermes update --gateway
    hermes  5678 ... hermes gateway restart

This is the missing diagnostic for #5646 / #6666 — we can prove
the restarts are from systemctl but can't determine WHO issues the
systemctl command. Next time it happens, the agent.log will contain
the evidence (the process that sent the signal or called systemctl
should still be alive when the handler fires).

gateway/run.py

@@ -9273,6 +9273,29 @@ async def start_gateway(config: Optional[GatewayConfig] = None, replace: bool =
         nonlocal _signal_initiated_shutdown
         _signal_initiated_shutdown = True
         logger.info("Received SIGTERM/SIGINT — initiating shutdown")
+        # Diagnostic: log all hermes-related processes so we can identify
+        # what triggered the signal (hermes update, hermes gateway restart,
+        # a stale detached subprocess, etc.).
+        try:
+            import subprocess as _sp
+            _ps = _sp.run(
+                ["ps", "aux"],
+                capture_output=True, text=True, timeout=3,
+            )
+            _hermes_procs = [
+                line for line in _ps.stdout.splitlines()
+                if ("hermes" in line.lower() or "gateway" in line.lower())
+                and str(os.getpid()) not in line.split()[1:2]  # exclude self
+            ]
+            if _hermes_procs:
+                logger.warning(
+                    "Shutdown diagnostic — other hermes processes running:\n  %s",
+                    "\n  ".join(_hermes_procs),
+                )
+            else:
+                logger.info("Shutdown diagnostic — no other hermes processes found")
+        except Exception:
+            pass
         asyncio.create_task(runner.stop())
 
     def restart_signal_handler():