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

[markovejnovic]

Summary

• hm.py.uv() namespace in both Python and TypeScript DSLs — a dedicated uv-managed Python project toolchain with run(), build(), lock_check()/lockCheck(), and publish() methods beyond the existing test/lint/fmt/typecheck surface.
• .harmont/ci.py — dogfood pipeline that uses hm.py.uv() for Python DSL checks and hm.rust() for Cargo workspace build/test/clippy/fmt.

New API

Python DSL:

project = hm.py.uv(path="dsls/harmont-py")
project.test()       # uv run pytest
project.lint()       # uv run ruff check .
project.run("cmd")   # uv run <cmd> (escape hatch)
project.build()      # uv build
project.lock_check() # uv lock --check

TypeScript DSL:

const project = py.uv({ path: "." });
project.test();      // uv run pytest
project.run("cmd");  // uv run <cmd>
project.lockCheck(); // uv lock --check

Existing hm.python() is unchanged — backwards compatible.

Pipeline DAG

scratch ─ :rust: apt-base ─ :rust: rustup ──┬─ build
                                             ├─ test
                                             ├─ clippy
                                             └─ fmt

scratch ─ :python: apt ─ uv-install ─ uv-sync ─┬─ lint
                                                 ├─ fmt
                                                 ├─ typecheck
                                                 └─ test

Test plan

• 23 new Python DSL tests (test_py_uv.py) — all pass, 399 total no regressions
• 19 new TypeScript DSL tests (py/uv.test.ts) — all pass, 278 total no regressions
• tsc --noEmit clean
• ruff check clean on new files
• CI green