feat: support TMDB episode group (g=) in explicit media tags and custom identifiers

- Add episode_group (g=) parameter parsing to explicit media tags in both Python and Rust metainfo parsers
- Propagate episode_group through MetaInfo, MetaBase, MediaInfo, and context models
- Update SKILL.md and update_custom_identifiers.py docs to describe episode group usage
- Add tests for episode_group recognition in metainfo and chain recognition logic

tests/test_episode_group_recognition.py

@@ -0,0 +1,37 @@
+import sys
+from types import ModuleType
+from unittest.mock import patch
+
+sys.modules.setdefault("qbittorrentapi", ModuleType("qbittorrentapi"))
+setattr(sys.modules["qbittorrentapi"], "TorrentFilesList", list)
+sys.modules.setdefault("transmission_rpc", ModuleType("transmission_rpc"))
+setattr(sys.modules["transmission_rpc"], "File", object)
+sys.modules.setdefault("psutil", ModuleType("psutil"))
+
+from app.chain import ChainBase
+from app.core.context import MediaInfo
+from app.core.meta import MetaBase
+from app.schemas.types import MediaType
+
+
+def test_recognize_media_uses_meta_episode_group():
+    """
+    识别链未显式传 episode_group 时，应沿用元数据中识别出的剧集组。
+    """
+    group_id = "5ad0ec240e0a26303f00d84d"
+    chain = ChainBase()
+    meta = MetaBase("测试剧集")
+    meta.name = "测试剧集"
+    meta.type = MediaType.TV
+    meta.episode_group = group_id
+    mediainfo = MediaInfo(title="测试剧集", year="2024", tmdb_id=100, type=MediaType.TV)
+
+    with patch.object(chain, "run_module", return_value=mediainfo) as run_module, patch(
+        "app.chain.MediaRecognizeShareHelper.report",
+        return_value=True,
+    ), patch("app.chain.MediaRecognizeShareHelper.query") as query_mock:
+        result = chain.recognize_media(meta=meta, cache=False)
+
+    assert result is mediainfo
+    assert run_module.call_args.kwargs["episode_group"] == group_id
+    query_mock.assert_not_called()