Python(chore): add uv for dev

[alexluck-sift]

Summary

• Migrate the Python dev workflow and CI from pip install + venv/ to uv: python/scripts/dev bootstraps via uv sync --extra dev-all, every subcommand runs through uv run, and pre-push hooks (extras.sh, fmt-lint.sh, stubs.sh, lock.sh) follow suit.

• Commit uv.lock so dev and CI share a single resolved dependency set. Fork resolution across python_version < '3.9', == '3.9.*', and >= '3.10' ([tool.uv].environments) lets each minor pick its own valid solution — 3.8 lands on numpy 1.24 + rosbags 0.9.23, 3.10+ on numpy 2.x + rosbags 0.11.2 — without the lockfile having to find a single set that fits the whole range.

• python_ci.yaml: a static-checks job (lint/format/mypy/pyright/stubs/extras/stubtest + uv lock --check) plus a matrix test-python job that syncs from the lockfile and runs pytest under the 3.8 floor interpreter. Adds a mypy --platform=win32 pass to catch Windows-only stub breakage (e.g. fcntl).

• Add test-floor (3.8) and test-ceiling (3.14) dev subcommands for local floor/ceiling exercises.

• Mark optional extras with their real version floors: rosbags ; python_full_version >= '3.8.2' (rosbags 0.9.23's lower bound), and docs entries with python_version >= '3.10' so the <3.10 forks resolve without docs tooling. Base requires-python stays at >=3.8.

• Add a mypy override for alive_progress to neutralize its overly tight alive_it stubs.

[github-actions]

Python docs preview: https://sift-stack.github.io/sift/python/pr-581/

Deployed from a8e6cae. The link may take up to a minute to become live as GitHub Pages propagates.