Summary

• Add a six-phase PostgreSQL loader compatibility scenario map and executable accept/reject corpus.
• Fix parser/catalog compatibility gaps around zero-column relations, function identity lists, FK equality compatibility, variadic/polymorphic resolution, CTE/LATERAL scope, partition index attach, and dependency recording.
• Add PostgreSQL 17 oracle coverage for loader compatibility accept/reject cases and remove the now-fixed pgregress known failure.

Test Plan

• go test ./pg/... -count=1
• go test -tags=oracle ./pg/catalog -run 'TestLoaderCompatPG17Oracle(Accepts|Rejects)Corpus' -count=1