fix(cargo-heather): preserve CRLF line endings in --fix mode

[Vaiz]

The internal helpers all use .lines() (which strips both \n and \r\n) followed by .join("\n"), silently converting CRLF files to LF when --fix rewrites them. This is especially problematic on Windows where git may be configured with core.autocrlf = true.

Fix: detect the line-ending style at the process::fix() entry point and thread it through every formatting and reassembly helper so they emit the correct separator natively. When the header is already correct, the original bytes are written unchanged.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.38202% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.0%. Comparing base (93c6346) to head (a1b59e9).

Files with missing lines	Patch %	Lines
crates/cargo-heather/src/checker/strip.rs	83.3%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #31     +/-   ##
=======================================
+ Coverage   89.4%   90.0%   +0.6%     
=======================================
  Files         15      15             
  Lines        756     808     +52     
=======================================
+ Hits         676     728     +52     
  Misses        80      80             

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[github-actions]

⚠️ Breaking Changes Detected

--- failure method_parameter_count_changed: pub method parameter count changed ---

Description:
A publicly-visible method now takes a different number of parameters, not counting the receiver (self) parameter.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#fn-change-arity
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.46.0/src/lints/method_parameter_count_changed.ron

Failed in:
  cargo_heather::CommentStyle::format_header now takes 2 parameters instead of 1, in /home/runner/work/ox-tools/ox-tools/crates/cargo-heather/src/comment.rs:125

If the breaking changes are intentional then everything is fine - this message is merely informative.

Remember to apply a version number bump with the correct severity when publishing a version with breaking changes (1.x.x -> 2.x.x or 0.1.x -> 0.2.x).

[Copilot]

Pull request overview

This PR updates cargo-heather’s --fix path to preserve the input file’s line-ending style (CRLF vs LF) when rewriting/adding license headers, addressing unintended CRLF→LF normalization especially on Windows setups.

Changes:

• Detect the input file’s line-ending style in process::fix() and thread it through internal formatting/reassembly helpers.
• Update header formatting and reassembly helpers to join lines with the detected separator instead of hard-coded "\n".
• Add regression tests to ensure CRLF/LF preservation and byte-equivalence when no changes are needed.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
crates/cargo-heather/src/process.rs	Detect line endings in fix(), thread into checker, and add CRLF/LF preservation tests.
crates/cargo-heather/src/comment.rs	Change header formatting to join with a provided line ending.
crates/cargo-heather/src/checker/strip.rs	Preserve line endings in header stripping/reassembly helpers by using the provided separator.
crates/cargo-heather/src/checker/mod.rs	Thread detected line ending through fix() and header prepending logic.

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