Type-defining instructions the codec doesn't model structurally -- OpTypeImage,
OpTypeSampler, OpTypeSampledImage, OpTypeMatrix, OpTypeOpaque, OpTypeEvent,
OpTypeDeviceEvent, OpTypeReserveId, OpTypeQueue, OpTypePipe -- decode to
Type{.OPAQUE} plus an Opaque_Info{opcode, words} side entry (the operand words
after the result <id>) and re-emit verbatim. One generic fallback covers every
opaque SPIR-V type byte-exact, with no per-type fields.
Test: image_type (OpTypeImage, 7 operands) round-trips -> 9 passed.
c2a5091336