duplicates: write type annotations

[9999years]

Description

This adds type annotations to beetsplug.duplicates.

To Do

• Documentation. (If you've added a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst to the bottom of one of the lists near the top of the document.)
• Tests. (Very much encouraged but not strictly required.)

[github-actions]

Thank you for the PR! The changelog has not been updated, so here is a friendly reminder to check if you need to add an entry.

[Copilot]

Pull request overview

This pull request adds type annotations to the beetsplug/duplicates.py plugin to improve type safety and code documentation.

Changes:

• Added from __future__ import annotations and imported typing utilities (TYPE_CHECKING, Any, DefaultDict, Iterator, Tuple, TypeAlias, cast)
• Added type aliases Tiebreak and KeyValues to document complex types used throughout the code
• Added type annotations to method signatures including _dup, _process_item, _checksum, _group_by, _order, _merge_albums, and _duplicates
• Added type annotations to local variables in the _dup function with # type: ignore comments
• Fixed variable shadowing issue in _duplicates method by renaming loop variable from objs to grouped_objs

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[Copilot]

Missing type annotations for the objs parameter and return type. Based on the implementation and similar method _merge_albums, the signature should be def _merge_items(self, objs: list[Item]) -> list[Item]:.

Suggested change

	def _merge_items(self, objs):
	def _merge_items(self, objs: list[Item]) -> list[Item]:

[codecov]

Codecov Report

❌ Patch coverage is 26.31579% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.75%. Comparing base (9b1bd5d) to head (bc2a94c).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
beetsplug/duplicates.py	26.31%	28 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6307      +/-   ##
==========================================
- Coverage   68.76%   68.75%   -0.01%     
==========================================
  Files         140      140              
  Lines       18610    18617       +7     
  Branches     3051     3052       +1     
==========================================
+ Hits        12797    12801       +4     
- Misses       5165     5168       +3     
  Partials      648      648              

Files with missing lines	Coverage Δ
beetsplug/duplicates.py	21.51% <26.31%> (+1.51%)	⬆️

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