Prove DTO and rich-value unary hydration

Parent

Applications have copyable plain-DTO and paired-codec hydration patterns with stable domain representations.

Prove a Schema class method and a rich scalar/binary value across actual dehydration/hydration and later browser refetch.
Keep plain DTO representation an explicit independent recipe and correct structural-cloning claims.
Failed queries remain omitted by default; safe error/Cause serialization is deliberate.
Prove synchronous codec callbacks and, where needed, an application-owned preparation stage that finishes async encoding before snapshot publication and decoding before hydration.
Effects/Promises do not enter query data; residual services remain explicit and caller-owned.
Adopt a unary helper only if it demonstrably removes meaningful repeated code, with public contract evidence; otherwise record the usable recipe decision.