- Add section 9 to data-sources-inventory.md covering live API quirks:
Eurostat SDMX city labels response shape, ONS CSV download path (observations
API 404s), US Census ACS place endpoint, GeoNames cities15000 bulk format
- Add population coverage summary table and DuckDB glob limitation note
- fix(extract): census_usa + geonames write empty placeholder when credentials
absent so SQLMesh staging models don't fail with "no files found"
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Move historical docs from docs/ and .claude/ to research/. Add superseded
notice to research/PLAN.md. Add CHANGELOG entries for previous fixes.
New: PROJECT.md (task tracker), docs/MARKETING.md (marketing strategy).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
