Rounds 18-26: RFC-0201 v5.23 adversarial review fixes

Comprehensive fixes across 9 review rounds covering CRIT, HIGH, MED, and LOW
issues. Key changes: validate_schema/validate_col_type at registration time,
MAX_CONTAINER_ELEMENTS constant, dispatch_struct debug_assert-only, return-order
convention documentation, deserialize_dmat overflow guard, Dmat zero-dimension
checks, BYTEA[] array support, serialize_dvec count bounds, ALTER TABLE BYTEA
rejection, version history reconstruction, test coverage for field_id prefix
pattern, depth propagation, and round-trip serialization.

Author: mmacedoeu