Fix op checkpoint JSONB binding

[uncfreak1255-code]

Summary

• Fix recordCompleted so op_checkpoints.completed_keys is written as a real JSONB array on Postgres, not a double-encoded scalar string.
• Add PGLite and real-Postgres regression coverage for the completed_keys shape.
• Tighten the JSONB static guard for executeRawDirect and fix the admin build gate that was timing out in verify.

Proof

• bun run verify -> 30/30 checks green
• bun test test/op-checkpoint.test.ts -> 31 pass, 0 fail
• Fresh Postgres pgvector/pgvector:pg16 E2E: DATABASE_URL=postgresql://postgres:postgres@localhost:5435/gbrain_test bun test test/e2e/op-checkpoint-jsonb-postgres.test.ts -> 1 pass, 0 fail
• Direct Postgres readback: array|chunk-a|2

Notes

Compared with upstream PR #2288, this keeps the fix narrow but avoids passing a bare top-level JS array into $3::jsonb; the value is wrapped in an object and extracted server-side with ($3::jsonb)->'completed_keys'.

[uncfreak1255-code]

Closing this one because it was opened from the fork master lineage and includes unrelated fork history. I am rebuilding the branch from upstream/master and will reopen a narrow PR.