Add comprehensive test coverage for the schema package including
Schema validation, JSON Schema Draft 7 compilation, document validation,
database serialization, and custom Type marshaling.
Tests cover:
- Schema.Valid() with various schema types (string, object, array, etc.)
- Schema.GetValidator() compilation
- Schema.ValidateString/ValidateBytes/ValidateGo with valid and invalid docs
- Schema.Value()/Scan() database serialization round-trip
- Type.MarshalJSON() including object auto-properties and ExtProps
- Type.UnmarshalJSON() including ExtProps extraction
- Pattern, enum, and array constraint validation
- scanFromJSON helper with string, bytes, and error cases