Migrate requirements files to PEP 735 dependency groups

[tpvasconcelos]

Description

Move all development dependencies from requirements/*.txt files into PEP 735 [dependency-groups] in pyproject.toml, making pyproject.toml the single source of truth for project metadata and dev dependencies. This is the "Manage the Python project" item from #219.

Changes:

• pyproject.toml: new [dependency-groups] table with cicd_utils, tests, docs, typing, and local-dev groups. The -r foo.txt includes from the old requirements files are expressed with { include-group = "..." }, and all comments (incl. the kaleido pin TODO) are preserved.
• tox.ini: environments now use tox's native dependency_groups setting instead of deps = -r requirements/*.txt (hence requires = tox>=4.22 + tox-uv>=1.17). In the base [testenv] section, the tests group is scoped with factor conditionals (pytest,tests,coverage: tests) so that build-dists and pre-commit-* don't inherit test dependencies (verified locally: .tox/build-dists does not contain pytest).
• Makefile: make install now runs uv pip install --editable . --group local-dev (the editable install used to live inside local-dev.txt).
• .readthedocs.yaml: uses Read the Docs' native uv support (added April 2026): method: uv, command: sync, groups: [docs] replaces the two pip-based install steps. The RTD build for this PR should validate this.
• MANIFEST.in: dropped the requirements/ include; requirements/*.txt files deleted.

Notes:

• No behavior change in dependency resolution: dependencies remain unpinned, same as the old requirements files. Committing a uv.lock for reproducible dev/CI environments is a possible follow-up, tracked in Investigate full adoption of uv #219.
• The dependabot pip ecosystem config keeps working against pyproject.toml (there was nothing version-pinned in the requirements files for it to bump anyway).
• Locally validated: uv pip install --dry-run -e . --group local-dev resolves; tox -e pytest runs green; tox --notest -e typing,release-notes,docs-static,build-dists all build their envs with exactly the expected dependencies; all pre-commit hooks pass (incl. validate-pyproject, check-readthedocs, and check-manifest).

Related issues

Related to #219.

PR check list

• Read the contributing guidelines.
• Provided the relevant details in the PR's description.
• Referenced relevant issues in the PR's description.
• Added tests for all my changes. (N/A - packaging/CI config only; validated via tox + pre-commit + the RTD build on this PR)
• Updated the docs for relevant changes. (N/A - the contributing guide's make init workflow is unchanged)
• Changes are documented in docs/reference/changelog.md.
• The CI check are all passing, or I'm working on fixing them!
• I have reviewed my own code! 🤠

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📚 Documentation preview 📚: https://ridgeplot--388.org.readthedocs.build/en/388/

[tpvasconcelos]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in 51a14bd. The only true conflict was requirements/tests.txt (deleted in this PR, modified in main) — kept the deletion since this PR migrates all deps to PEP 735 dependency groups. The tox.ini auto-merged cleanly, picking up the coverage threshold bumps (95→100% unit, 98→100% combined) from main while preserving the dependency_groups approach.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (14e872d) to head (ac819a3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           19        19           
  Lines          674       674           
  Branches        88        88           
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  Hits           674       674           

Flag	Coverage Δ
combined-src	100.00% <ø> (ø)

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