tests/ (Python backend tests, .mjs frontend rule tests) is no longer
ignored. tools/run_tests.mjs runs the structure check, every
tests/*.mjs and the Python tests with $PYTHON, the portable
python_embeded or python. docs/guides/testing.md says how to run and
write them; README links it. Developer notes no longer point at 18 test
files that were removed earlier (AGENTS.md table, backend, frontend and
update-guide notes).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
