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-app/src/tavolo/app.py

@@ -46,6 +46,7 @@ from tavolo.briscola import (
 )
 from tavolo.platform import GameRegistry, Platform, PlatformMixin
 from tavolo.platform.deadlines import DeadlineScheduler, DeadlineSchedulerMixin
+from tavolo.platform.openapi import SCHEMAS
 from tavolo.platform.store import GameStore, InMemoryGameStore, RedisGameStore
 from tavolo.platform.tortoise_mixin import TortoiseMixin
 from tavolo.scopa import ScopaEngine, ScopaQuattroEngine
@@ -218,6 +219,7 @@ openapi_mixin = OpenAPIMixin(
     description="Multiplayer card-game platform API",
     spec_path="/api/openapi.json",
     docs_path="/api/docs",
+    components={"schemas": SCHEMAS},
 )
 tortoise_mixin = TortoiseMixin(
     database_url=settings.database_url,