* build: replace the npm lint stack with pre-commit
markdownlint-cli2, prettier and eslint for YAML/JSON, husky and
lint-staged are gone. pre-commit runs ruff, rumdl (the same five
markdown rules), yamllint, yamlfix, the JSON checks, both validators
and pytest, at commit time and over the whole tree from
tools/quality.py, which is now what `npm run quality` calls. ESLint and
prettier stay only for the docs-site scripts and tests. quality.yaml
collapses to a Python job and a docs-site job.
yamlfix keeps one blank line and no document-start marker: its defaults
strip blank lines inside block scalars and add `---`, which the sprint
status scripts do not write back. The JSON hook keeps key order and
non-ASCII text.
* style: apply yamlfix and JSON formatting to the tree
Mechanical output of the new hooks; every file parses to the same data.
* docs: state what the commit hook covers
Alex Verkhovsky