Type musicbrainz (#6329)

## Add full type coverage to the MusicBrainz plugin

This PR introduces complete static typing for
`beetsplug/musicbrainz.py`, `beetsplug/mbpseudo.py`, and
`beetsplug/_utils/musicbrainz.py`, and enforces it via `mypy` strict
mode.

### Key changes

**New `TypedDict` schema in `beetsplug/_utils/musicbrainz.py`**

A comprehensive set of `TypedDict` classes now models the full
MusicBrainz API response surface — `Release`, `Recording`, `Track`,
`ReleaseGroup`, `Artist`, `ArtistCredit`, `Work`, and all relation
types. Public API methods (`get_release`, `get_recording`, etc.) now
return these typed shapes instead of the opaque `JSONDict`.

**Key normalization: dash-to-underscore**

The internal `_normalize_data` method (previously `_group_relations`)
now also converts all hyphenated keys (e.g. `artist-credit`,
`release-group`, `sort-name`) to underscored equivalents (e.g.
`artist_credit`, `release_group`, `sort_name`) at parse time. This makes
the data structure Python-idiomatic and is what allows the `TypedDict`
definitions to use clean attribute names. All downstream field accesses,
test fixtures, and JSON test resources are updated accordingly.

**`mypy` strict mode enabled** for the three affected modules via
`setup.cfg`.

### Impact

- No behaviour change for end users — this is purely an internal
refactor.
- Code reading the MusicBrainz response now has IDE completion and
type-checking support.
- The normalization boundary is clearly established at
`_normalize_data`, so callers never see raw hyphenated keys.
- Test fixtures and resource JSON files are updated to match the new
normalized shape.

Author: snejus

beetsplug/_utils/musicbrainz.py

@@ -299,7 +299,7 @@ def get_track_info(self, tracks):
                 identifier, includes=["releases", "artist-credits"]
             )
             title = recording.get("title")
-            artist_credit = recording.get("artist-credit", [])
+            artist_credit = recording.get("artist_credit", [])
             if artist_credit:
                 artist = artist_credit[0].get("artist", {}).get("name")
             else:

beetsplug/listenbrainz.py

@@ -101,7 +101,7 @@ def id(self) -> str:
     @property
     def release_count(self) -> int:
         """Total number of releases recorded in the collection."""
-        return self.data["release-count"]
+        return self.data["release_count"]
 
     @property
     def releases_url(self) -> str:
@@ -173,7 +173,7 @@ def collection(self) -> MBCollection:
         # Get all release collection IDs, avoiding event collections
         if not (
             collection_by_id := {
-                c["id"]: c for c in collections if c["entity-type"] == "release"
+                c["id"]: c for c in collections if c["entity_type"] == "release"
             }
         ):
             raise ui.UserError("No release collection found.")

beetsplug/mbcollection.py

@@ -41,7 +41,12 @@
     from beets.autotag.distance import Distance
     from beets.autotag.hooks import AlbumMatch
     from beets.library import Item
-    from beetsplug._typing import JSONDict
+
+    from ._utils.musicbrainz import (
+        Release,
+        ReleaseRelation,
+        ReleaseRelationRelease,
+    )
 
 _STATUS_PSEUDO = "Pseudo-Release"
 
@@ -133,7 +138,7 @@ def candidates(
                     yield album_info
 
     @override
-    def album_info(self, release: JSONDict) -> AlbumInfo:
+    def album_info(self, release: Release) -> AlbumInfo:
         official_release = super().album_info(release)
 
         if release.get("status") == _STATUS_PSEUDO:
@@ -161,30 +166,32 @@ def album_info(self, release: JSONDict) -> AlbumInfo:
         else:
             return official_release
 
-    def _intercept_mb_release(self, data: JSONDict) -> list[str]:
+    def _intercept_mb_release(self, data: Release) -> list[str]:
         album_id = data["id"] if "id" in data else None
         if self._has_desired_script(data) or not isinstance(album_id, str):
             return []
 
         return [
             pr_id
-            for rel in data.get("release-relations", [])
+            for rel in data.get("release_relations", [])
             if (pr_id := self._wanted_pseudo_release_id(album_id, rel))
             is not None
         ]
 
-    def _has_desired_script(self, release: JSONDict) -> bool:
+    def _has_desired_script(
+        self, release: Release | ReleaseRelationRelease
+    ) -> bool:
         if len(self._scripts) == 0:
             return False
-        elif script := release.get("text-representation", {}).get("script"):
+        elif script := release.get("text_representation", {}).get("script"):
             return script in self._scripts
         else:
             return False
 
     def _wanted_pseudo_release_id(
         self,
         album_id: str,
-        relation: JSONDict,
+        relation: ReleaseRelation,
     ) -> str | None:
         if (
             len(self._scripts) == 0
@@ -206,19 +213,17 @@ def _wanted_pseudo_release_id(
             return None
 
     def _replace_artist_with_alias(
-        self,
-        raw_pseudo_release: JSONDict,
-        pseudo_release: AlbumInfo,
+        self, raw_pseudo_release: Release, pseudo_release: AlbumInfo
     ):
         """Use the pseudo-release's language to search for artist
         alias if the user hasn't configured import languages."""
 
         if len(config["import"]["languages"].as_str_seq()) > 0:
             return
 
-        lang = raw_pseudo_release.get("text-representation", {}).get("language")
-        artist_credits = raw_pseudo_release.get("release-group", {}).get(
-            "artist-credit", []
+        lang = raw_pseudo_release.get("text_representation", {}).get("language")
+        artist_credits = raw_pseudo_release.get("release_group", {}).get(
+            "artist_credit", []
         )
         aliases = [
             artist_credit.get("artist", {}).get("aliases", [])