Documentation: Repo tooling setup

Capability docs

Capability doc	What changed	History row
repo-tooling	New: the Python project, hooks, CI, PyPI releases and docs site	issue-2
capabilities index	Row added for repo-tooling	n/a (index)
dev-environment	Unchanged: it covers the agent setup (instructions, Claude settings, .the-loop/), which this item does not change	—

Documentation

Document	What changed
README.md	Usage example, install, two-line dev setup, links to the docs site and local-development guide
docs/index.md	New: docs-site home page
docs/guide/tech-stack.md	New: tools, where each is configured, how checks flow, repository layout
docs/guide/local-development.md	New: prerequisites, uv sync, installing the pre-commit hooks, running each check, docs workflow
docs/guide/releasing.md	New: how versions are computed, what release.yml does, required GitHub/PyPI settings
docs/specs/index.md	New: landing page for the specs tree
Docs site (all pages)	Mermaid fences render as diagrams (vitepress-plugin-mermaid), requested in PR #5 review
docs/architecture/architecture.md	Repository layout and tooling section
docs/decisions/decision-001.md, decisions.md	New decision record and index row