Support division-specific ruleset events and game configs

[KyleHerndon]

Summary

• add policy_membership_events as a division/stage ruleset hook alias for membership transitions
• add division/stage game_config overrides that are emitted on scheduled episode requests
• make episode timeout/throttle logic prefer per-episode game config when present

Validation

• No repo lint command is configured in pyproject.toml/README; ran git diff --cached --check before commit and it passed.
• uv run pytest tests/test_commissioner_strategies.py tests/test_commissioner_websocket.py::test_configured_episode_timeout_prefers_game_duration_from_ticks tests/test_commissioner_websocket.py::test_configured_episode_timeout_reads_round_timeout_seconds tests/test_commissioner_websocket.py::test_configured_episode_timeout_reads_explicit_nested_duration tests/test_commissioner_websocket.py::test_episode_duration_limit_has_five_minute_floor tests/test_commissioner_websocket.py::test_episode_duration_limit_doubles_timeout tests/test_commissioner_websocket.py::test_episode_duration_limit_doubles_ten_minute_round_timeout tests/test_commissioner_websocket.py::test_episode_duration_limit_prefers_episode_game_config -q
• Note: the full websocket TestClient suite hangs in this environment even with a minimal FastAPI TestClient app, so I validated the non-TestClient timeout helpers plus the full ruleset strategy suite.