docs: clarify gateway service scopes (#1378)

hermes_cli/cron.py

@@ -96,6 +96,7 @@ def cron_list(show_all: bool = False):
     if not find_gateway_pids():
         print(color("  ⚠  Gateway is not running — jobs won't fire automatically.", Colors.YELLOW))
         print(color("     Start it with: hermes gateway install", Colors.DIM))
+        print(color("                    sudo hermes gateway install --system  # Linux servers", Colors.DIM))
         print()
 
 
@@ -120,7 +121,8 @@ def cron_status():
         print(color("✗ Gateway is not running — cron jobs will NOT fire", Colors.RED))
         print()
         print("  To enable automatic execution:")
-        print("    hermes gateway install    # Install as system service (recommended)")
+        print("    hermes gateway install    # Install as a user service")
+        print("    sudo hermes gateway install --system  # Linux servers: boot-time system service")
         print("    hermes gateway            # Or run in foreground")
 
     print()

hermes_cli/main.py

@@ -2313,7 +2313,7 @@ Examples:
     hermes gateway                Run messaging gateway
     hermes -s hermes-agent-dev,github-auth
     hermes -w                     Start in isolated git worktree
-    hermes gateway install        Install as system service
+    hermes gateway install        Install gateway background service
     hermes sessions list          List past sessions
     hermes sessions browse        Interactive session picker
     hermes sessions rename ID T   Rename/title a session