Preferred way of encoding fixed-width opaque byte buffers?

I think the answer is `(repeat 32 :byte)` which mostly works except for the part where it interacts poorly with other byte types, since you're forcing it to be a seq.

Start by examining how `(repeat 32 :byte)` is handled and where it interacts with other byte types. Reproduce the reported sequence behavior, then clarify the preferred fixed-width opaque-buffer representation and define the expected behavior that would count as done.

Written by the indexing model from the issue text.