Add PROMPT_SELECTION.md (prompt-selection methodology)

README: document PROMPT_SELECTION.md

Update Croissant to RAI-rich version with prov:wasGeneratedBy activities

Enrich NExT-QA citation: pages, arXiv, full venue name

Fix NExT-QA author name: Xun -> Xindi

Initial NExT-CF v1.0.0 release

initial commit