feat: support Python 3.15

[chenrui333]

Extend the Python requirement to include 3.15 and refresh the lockfile's Python range without changing dependency versions.

The 167 upstream tests pass on Python 3.15 with Homebrew's packaged dependencies, and source builds plus the CLI check pass on macOS and Linux.

Closes #103.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.39%. Comparing base (0ed0c20) to head (5636cac).
⚠️ Report is 36 commits behind head on main.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #104      +/-   ##
==========================================
+ Coverage   90.09%   90.39%   +0.30%     
==========================================
  Files         105      106       +1     
  Lines        3464     3552      +88     
==========================================
+ Hits         3121     3211      +90     
+ Misses        343      341       -2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.