Document every API response body in the OpenAPI spec

kaya-openapi 0.0.8 supports named component schemas, so the routes'
description-only responses become $refs: schemas for the core payloads
(auth providers, lobby, game view, ongoing games, match history,
leaderboard, ratings) live in tavolo.platform.openapi and are registered
through the mixin's components. Engine-defined parts (options echo, game
views, match results) stay open objects on purpose. Error responses now
carry the error envelope schema, and a new suite sweeps the document to
keep every /api response typed.

server/packages/tavolo-platform/tests/helpers.py

@@ -45,6 +45,7 @@ from tavolo.platform import (
 )
 from tavolo.platform.auth import get_ws_user  # noqa: F401  (re-exported for patching)
 from tavolo.platform.deadlines import DeadlineScheduler
+from tavolo.platform.openapi import SCHEMAS
 from tavolo.platform.registry import GameRegistry
 from tavolo.platform.store import InMemoryGameStore
 from tavolo.platform.tortoise_mixin import TortoiseMixin
@@ -253,6 +254,7 @@ def make_platform(
         description="test app",
         spec_path="/api/openapi.json",
         docs_path="/api/docs",
+        components={"schemas": SCHEMAS},
     )
     scheduler = DeadlineScheduler(
         game_store,