Browsing misc response models

[sigma67]

Part of #307. Base branch: ytmusicapi-2. Read the contributor guide from #982 before starting.

The remaining browsing endpoints not covered by the core entity models.

Scope

mixins/browsing.py, parsed by ytmusicapi/parsers/browsing.py:

• get_home
• get_user, get_user_playlists, get_user_videos
• get_song, get_song_related, get_song_credits
• get_tasteprofile

Watch out for

• get_home returns mixed shelf contents — songs, albums, playlists, artists in one list. parse_content_list skips renderer types it does not recognise (fix: skip unexpected renderer types in parse_content_list #970); the model must tolerate heterogeneous shelves.
• get_song returns the raw player response and differs from the song model in Song/Video playlist-item model #983. Do not conflate them.
• get_tasteprofile returns a mapping keyed by artist name rather than a list.

Definition of done

• All listed methods return models.
• mypy --strict clean.