Summary

• Table Browser and SQL results encode cells as PG literals: ISO timestamps, \x hex for bytea, JSON text for jsonb, {1,2,3} for arrays — not Object.toString.
• getTableSchema prefers udt_name so ARRAY / USER-DEFINED (enums, int[]) reach formatLiteral.
• Grid validator skips scalar int/json checks on array types.

Test plan

• Browse types_showcase.all_datetime — timestamptz is ISO, Save round-trips.
• Browse types_showcase.all_binary_and_bits — bytea shows \xdeadbeef, Save persists.
• Browse types_showcase.all_json_xml — jsonb is JSON text, not Dart Map.toString.
• Browse types_showcase.all_arrays — int[] shows {1,2,3,42,999}.
• Browse types_showcase.all_custom_entities — enum admin stays a quoted label on Save.

Closes #789