Panel plane: complete route (idempotent)

POST /api/v1/panel/instances/{id}/complete delegates to the core
completion layer (nestquest_core.completion.complete_instance) with
actor_source='panel' and the tapped actor_child_id, so the append
lock, actor validation, and idempotence all live in core. The route
maps only the unknown-instance ValueError to 404, guards the
child-mismatch case (complete_instance does not check that the tapped
profile owns the instance) with a 404 that does not leak existence,
and returns success on both the first call and the already-done
no-op — the CompletionResult.appended flag decides, so a retried tap
never writes a second event. The router's single require_panel_token
dependency covers auth; tests cover first call, idempotent repeat,
404, 401, wrong-child 404, and OpenAPI documentation.

Task: 1860ef76-e936-4d4f-a150-1cf7b721f519

api/nestquest_core.py

@@ -112,12 +112,17 @@ core_migrations = importlib.import_module(f"{_CORE_MODULE_NAME}.migrations")
 #: assembly the panel routes call.
 core_snapshot = importlib.import_module(f"{_CORE_MODULE_NAME}.snapshot")
 
+#: The completion service (``core.completion.complete_instance`` /
+#: ``uncomplete_instance``) the panel's write routes call.
+core_completion = importlib.import_module(f"{_CORE_MODULE_NAME}.completion")
+
 #: The explicit settings object (``core.settings.NestQuestSettings``)
 #: the snapshot builder's ``settings`` parameter takes.
 core_settings = importlib.import_module(f"{_CORE_MODULE_NAME}.settings")
 
 __all__ = [
     "core",
+    "core_completion",
     "core_db",
     "core_migrations",
     "core_snapshot",