Use lockless uv workflow for pure Python

[timkpaine]

Pilots an end-to-end uv workflow in the pure Python template without committing a Python lockfile.

• Moves development tools from the published develop extra to the PEP 735 dev dependency group.
• Installs that group with uv pip, preserving fresh resolution of compatible package versions and editable ecosystem workflows without generating uv.lock.
• Uses uv build for isolated sdist and wheel creation, then checks those artifacts with check-dist.
• Removes redundant build, Hatchling, Twine, uv, and wheel development dependencies and updates generated documentation.

Rendered the pure template with Copier under Python 3.12 and ran make develop, make lint, make checks, make test, and make dist. All passed, and no uv.lock was created.