Metadatasource cleanup docs

[semohr]

This PR includes documentation updates for the new metadatasource plugin architecture, as requested by @snejus. The docs changes were split out from the original implementation to keep things focused and reviewable.

• Introduces comprehensive documentation for the new metadata plugin system.
• Performs a general cleanup of the plugin-related developer documentation for clarity and consistency.

Note:
This PR should be reviewed and merged together with [#5787]

[Copilot]

Pull Request Overview

Documentation for the new metadatasource plugin architecture has been added and the legacy monolithic plugin guide has been split into focused sections.

• Introduces separate “commands,” “events,” and “other” plugin dev guides under docs/dev/plugins/.
• Cleans up cross-references and landing pages, including updates to docs/plugins/index.rst and docs/dev/index.rst.
• Updates API docs (docs/api/plugins.rst) to include new metadata plugin classes.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/plugins/index.rst	Updated link to point at the new plugin dev index
docs/dev/plugins/other.rst	Added “Extending the Autotagger” guide
docs/dev/plugins/index.rst	Created plugin development index with toctree
docs/dev/plugins/events.rst	Added event-listener documentation
docs/dev/plugins/commands.rst	Added CLI subcommand guide
docs/dev/plugins.rst	Removed outdated monolithic plugin dev guide
docs/dev/index.rst	Added Confuse link and updated plugin toctree path
docs/api/plugins.rst	Added metadata plugin classes to API autosummary

Comments suppressed due to low confidence (1)

docs/dev/plugins/other.rst:111

• Remove the extra backtick after the Sphinx reference. It should close as :py:meth:beets.plugins.BeetsPlugin.add_media_field() method.

your plugins :py:meth:`beets.plugins.BeetsPlugin.add_media_field()`` method.

[Copilot]

Replace "Than we will rank" with "Then we will rank" to correct the transition word.

Suggested change

	On metadata lookup, the autotagger will first call the :py:meth:`MetadataSourcePlugin.candidates` (or :py:meth:`MetadataSourcePlugin.item_candidates` ) method of all enabled MetadataSourcePlugins to get a list of available candidates. Than we will rank all candidates by using each plugins :func:`MetadataSourcePlugin.track_distance` and :py:meth:`MetadataSourcePlugin.album_distance` methods.
	On metadata lookup, the autotagger will first call the :py:meth:`MetadataSourcePlugin.candidates` (or :py:meth:`MetadataSourcePlugin.item_candidates` ) method of all enabled MetadataSourcePlugins to get a list of available candidates. Then we will rank all candidates by using each plugins :func:`MetadataSourcePlugin.track_distance` and :py:meth:`MetadataSourcePlugin.album_distance` methods.