Tighten prompt_template_source.notes: explicit 5-tier classification per 2026-06-01 priority rules

Refine prompt_template_source: cite verifiable official sources per 2026-05-30 deep audit

Populate prompt_template_source for all subsets per 2026-05-30 audit

Update metadata.json source.url keys to match new HF split names

Restore metadata.json

Restructure: revert to default config matching official upstream

initial commit