fix(check): expand env vars in rev_range arg

[ilitygergo]

Description

Checklist

• I have read the contributing guidelines

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Code Changes

• Add test cases to all the changes you introduce
• Run uv run poe all locally to ensure this change passes linter check and tests
• Manually test the changes:
  • Verify the feature/bug fix works as expected in real-world scenarios
  • Test edge cases and error conditions
  • Ensure backward compatibility is maintained
  • Document any manual testing steps performed
• Update the documentation for the changes

Documentation Changes

• Run uv run poe doc locally to ensure the documentation pages renders correctly
• Check and fix any broken links (internal or external)

Expected Behavior

The commitizen-branch pre-push hook should successfully validate commit messages
using the ref range provided by pre-commit via the PRE_COMMIT_FROM_REF and
PRE_COMMIT_TO_REF environment variables.

Steps to Test This Pull Request

1. Add the following to your .pre-commit-config.yaml:

   repos:
     - repo: https://github.com/commitizen-tools/commitizen
       rev: master
       hooks:
         - id: commitizen
           stages: [commit-msg]
         - id: commitizen-branch
           stages: [pre-push]

2. Install the pre-commit hooks:
   pre-commit install --hook-type pre-commit --hook-type commit-msg --hook-type pre-push
3. Make a commit with a valid conventional commit message:
   git commit -m "feat: my new feature"
4. Run git push — the commitizen-branch hook should pass instead of failing with:
   fatal: ambiguous argument '$PRE_COMMIT_FROM_REF..$PRE_COMMIT_TO_REF': unknown revision or path not in the working tree

Environment used for testing:

• Python 3.14.3
• commitizen 4.15.1
• pre-commit 4.6.0

Additional Context

The root cause is that pre-commit passes args directly to the process as a list
without shell interpolation, so $PRE_COMMIT_FROM_REF..$PRE_COMMIT_TO_REF arrives
as a literal string to cz check rather than being expanded to actual git SHAs.
Pre-commit does set these as environment variables in the hook process, so
os.path.expandvars() correctly resolves them at runtime.

Closes #1923
Closes #1912
Related to #704

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.23%. Comparing base (9707a58) to head (c05a03f).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1993   +/-   ##
=======================================
  Coverage   98.23%   98.23%           
=======================================
  Files          61       61           
  Lines        2779     2782    +3     
=======================================
+ Hits         2730     2733    +3     
  Misses         49       49           

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