GLSL_NV_mesh_shader confusion about storage layout qualifiers for perTaskNV

Is there language on how to define perTask-tagged blocks in SPIR-V? glslang is generating Offset and MatrixStride OpMemberDecorates for perTask-tagged ins/outs, as if they were SSBOs or UBOs, but the actual storage class is Input/Output. Nowhere else, I believe, does SPIR-V use storage decorations for anything other than UniformConstant, StorageBuffer, PushConstant or ShaderRecordBuffer.

All the mesh shader interface variable declarations seem unidiomatic and I'm not confident I can get things all right just by probing glslang.

Start by locating the SPIR-V Registry text covering GL_NV_mesh_shader and compare its perTaskNV interface rules with glslang output for Offset and MatrixStride decorations. Determine and document the normative storage-layout treatment for Input/Output perTask blocks; done when the specification resolves whether those decorations are valid and how such variables are declared.

Written by the indexing model from the issue text.