chore: Make nix hook optional

[kuznetsss]

High Level Overview of Change

This PR makes nix pre-commit hook optional in development environment and enforced only inside Github Actions.

Context of Change

Type of Change

• 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)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

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

This PR makes the nix pre-commit hook optional for local development environments while keeping it enforced in GitHub Actions CI. This allows developers without nix installed to run pre-commit hooks successfully, while still ensuring nix files are properly formatted in CI.

Changes:

• Modified the nix-fmt pre-commit hook to conditionally execute based on nix availability or GitHub Actions environment

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[ximinez]

Works on my end.

What do you think about running pre-commit with --verbose in the action?

[kuznetsss]

@ximinez, good idea! I've added --verbose in pre-commit call and updated action hash.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.8%. Comparing base (404f35d) to head (449dca4).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6431     +/-   ##
=========================================
- Coverage     79.8%   79.8%   -0.0%     
=========================================
  Files          848     848             
  Lines        67757   67757             
  Branches      7558    7559      +1     
=========================================
- Hits         54074   54063     -11     
- Misses       13683   13694     +11     

see 5 files with indirect coverage changes

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