feat: add hm.py.uv toolchain + dogfood CI pipeline #68

Job	Run time
harmont-ts (vitest + tsc)	16s
harmont-py (pytest + ruff + mypy) (3.12)	20s
dogfood (hm run ci)	2m 20s
cargo test --lib + clippy	52s
harmont-py (pytest + ruff + mypy) (3.11)	18s
docker-gated integration test	0s
	4m 6s

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