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: Apply 2026-05-19 audit template fix

fix: modalities taxonomy, task_type, url consolidation, structural corrections

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