Release phylib 2.7.1

[rossant]

Summary

Prepare phylib 2.7.1 for release.

• documents all changes since 2.7.0;
• fixes the existing flake8 violations and enforces lint in CI;
• sets the package version to 2.7.1;
• includes the phylib fixes required by Merge workspace, amplitude threshold splits, and curation workflow improvements phy#1404.

Validation

• local flake8: passed with flake8 7.3.0
• local tests: 280 passed on Python 3.12.14
• wheel and sdist: built successfully and passed twine check
• wheel smoke test: clean installation imported phylib 2.7.1 successfully

Release checklist

• Changelog includes all changes since 2.7.0
• Package version is 2.7.1
• Local flake8 passes
• Local test suite passes
• Wheel and sdist pass twine check
• Built wheel passes a clean installation and import smoke test
• GitHub CI passes
• Approved by @oliche
• PR merged
• Annotated 2.7.1 tag created from the merged release commit
• Release artifacts rebuilt from the tagged commit
• Artifacts uploaded to PyPI
• PyPI installation verified
• Downstream phy template-less waveform regression verified
• master bumped to 2.7.2.dev0

Merging, tagging, and publishing remain blocked until @oliche explicitly approves this PR.

[rossant]

Release preparation is complete and the full GitHub CI matrix is green, including lint and package build. The PR is now paused at the required @oliche approval gate; it will not be merged, tagged, or published before explicit approval.