Phase 3a: add a pre-commit standard to core:setup-repo

[jonnyspicer]

Adds a pre-commit standard to core:setup-repo for the Python and TS stacks, with CI as the single source of truth — lint/format/hygiene are defined once in .pre-commit-config.yaml and run both locally (git hook) and in CI. First half of Phase 3; the C++/CMake stack (Phase 3b) is a separate later sub-project.

What's added

• pre-commit configs (assets/precommit/): python.yaml (hygiene hooks + astral-sh/ruff-pre-commit: ruff --fix, ruff-format) and ts.yaml (hygiene hooks + a local npx eslint --fix hook). Both pin pre-commit-hooks@v5.0.0; python pins ruff-pre-commit@v0.8.0.
• CI = single source of truth: ci-python.yml and ci-node.yml now run uvx pre-commit run --all-files for lint/format/hygiene (the direct ruff check/ruff format and npm run lint steps are removed). Tests (pytest / typecheck + test) stay. The node CI gains a Python+uv step so it can run pre-commit.
• Engine: copies .pre-commit-config.yaml for python/ts stacks (not none).
• SKILL.md: install step registers the hook (uvx pre-commit install); CLAUDE.md guidance now points at pre-commit run --all-files as the lint/format command.
• Version bumped 0.4.0 → 0.5.0.
• New test-precommit-assets.sh (wired into this repo's CI) + updated CI/scaffold tests.

Out of scope: C++ (Phase 3b), prettier, typecheck-on-commit.

Verification

• All five suites pass (test-precommit-assets, test-python-assets, test-ci-assets, test-node-assets, test-scaffold) and claude plugin validate . passes.
• Real pre-commit run --all-files on freshly scaffolded temp repos: python (rc=0; hygiene passed, ruff skipped — no .py in the base scaffold) and ts-frontend (rc=0 after npm install; hygiene + eslint passed).

Process

Subagent-driven: fresh implementer per task, per-task spec+quality review with fixes, Opus whole-branch review (verdict: ready to merge). The validator was hardened to pin the hook revs, ruff --fix, and the eslint hook fields.

🤖 Generated with Claude Code