ci: Run pre-commit on diff in clang-tidy workflow

[mathbunnyru]

High Level Overview of Change

This:

• works well when some problems are not automatically fix-able (we won't fail for the wrong reason)
• gives a diff which already matches our style rules

Context of Change

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[Copilot]

Pull request overview

Updates the reusable clang-tidy GitHub Actions workflow to (a) detect whether clang-tidy produced any working-tree changes and (b) optionally run pre-commit to apply style fixes so the uploaded patch better matches repository formatting rules.

Changes:

• Adds a “Check for changes” step to detect whether clang-tidy produced a diff.
• Runs pre-commit style fixes when changes are detected, and switches diff artifact generation/upload gating to the “files changed” result.

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[godexsoft]

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.1%. Comparing base (e092c52) to head (c3ab4fd).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7078   +/-   ##
=======================================
  Coverage     82.1%   82.1%           
=======================================
  Files         1010    1010           
  Lines        76033   76033           
  Branches      7369    7366    -3     
=======================================
  Hits         62413   62413           
  Misses       13620   13620           

see 2 files with indirect coverage changes

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