Promote BlobHash to a named OpenAPI schema with the ^[0-9a-f]{64}$
pattern, reference it from WriteBlobResponse.hash and the blobHash path
parameter, and map it to fabro_types::BlobHash via with_replacement.
The server now serializes the domain type directly and the client gets
a parsed BlobHash by construction, removing the to_string/parse adapter
pair across the wire boundary. Adds the JSON-parity test required for
new replacements.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
88b2a01af8