fix(service): start the detached service without a console window on Windows

cli/service_cli.py

@@ -170,8 +170,13 @@ def _start_detached(
         stdout=subprocess.DEVNULL,
         stderr=subprocess.DEVNULL,
         start_new_session=os.name != "nt",
+        # CREATE_NO_WINDOW, not DETACHED_PROCESS: DETACHED_PROCESS makes Windows
+        # allocate a brand-new console for the service, which the default
+        # terminal surfaces as a visible window on every `service start`.
+        # CREATE_NO_WINDOW still runs without any window and still outlives the
+        # launcher (the console is private to the child, never inherited).
         creationflags=(
-            subprocess.DETACHED_PROCESS | subprocess.CREATE_NEW_PROCESS_GROUP
+            subprocess.CREATE_NO_WINDOW | subprocess.CREATE_NEW_PROCESS_GROUP
         )
         if os.name == "nt"
         else 0,

tests/app_server/test_service.py

@@ -213,7 +213,9 @@ def test_service_exits_cleanly_after_control_stop(tmp_path, log_to_file, detache
         cwd=Path(__file__).resolve().parents[2],
         start_new_session=detached and os.name != "nt",
         creationflags=(
-            subprocess.DETACHED_PROCESS | subprocess.CREATE_NEW_PROCESS_GROUP
+            # Mirror the launcher: CREATE_NO_WINDOW, so the detached leg does
+            # not pop a console window on Windows (DETACHED_PROCESS would).
+            subprocess.CREATE_NO_WINDOW | subprocess.CREATE_NEW_PROCESS_GROUP
             if detached and os.name == "nt"
             else 0
         ),