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.

• Preserves the published develop extra so test and development dependencies remain installable with built artifacts.
• Uses lockless uv pip commands for source development and dependency installation.
• 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 requirements, make develop, make lint, make checks, make test, and make dist. All passed, and no uv.lock was created.

Also installed the generated wheel with [develop] in a fresh environment outside the source checkout and ran its vendored test from site-packages successfully. Changes to artifact-test actions are intentionally out of scope.