fix(match): change match creation behavior to be multi-thread compliant

[mdevolde]

fix(match): change match creation behavior to be multi-thread compliant

Why the pull request was made

To ensure having a multi-thread compliant lib.

Summary of changes

• Make language_tool_python.Match.four_byte_char_positions public.
• language_tool_python.match.Match.__init__ now takes a four_byte_positions argument instead of text.
• Remove the Match.PREVIOUS_MATCHES_TEXT and Match.FOUR_BYTES_POSITIONS class attributes (using insteead four_byte_positions arg).
• In language_tool_python.server.LanguageTool.check, create Match with this new signature.

Screenshots (if appropriate):

Not applicable.

How has this been tested?

Applied local tests.

Resources

Not applicable.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Chore / maintenance (non-breaking change that does not affect functionality, such as updating dependencies or fixing typos)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters, checked types and tests.
• Added your changes to the CHANGELOG file, if applicable.

[Copilot]

Pull request overview

This PR updates how Match objects are constructed to avoid shared mutable class-level state, making offset adjustment for 4-byte UTF-8 characters safe under concurrent .check() calls.

Changes:

• Exposes four_byte_char_positions() publicly and reuses it in LanguageTool.check().
• Refactors Match.__init__ to accept precomputed four_byte_positions instead of the original text, removing the previous class-level cache.
• Updates CHANGELOG.md to document the new public helper and the breaking constructor change.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/language_tool_python/server.py	Precomputes 4-byte char positions once per .check() call and passes them into Match.
src/language_tool_python/match.py	Makes 4-byte char position helper public and changes Match construction to avoid shared class state.
CHANGELOG.md	Documents the new public helper, the breaking API change, and the concurrency bug fix.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.67%. Comparing base (3ebb352) to head (a03e122).
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #213      +/-   ##
==========================================
+ Coverage   80.66%   80.67%   +0.01%     
==========================================
  Files          13       13              
  Lines        1769     1770       +1     
==========================================
+ Hits         1427     1428       +1     
  Misses        342      342              

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