The validation report overloads the describedby relation

[tophcodes]

What

The validation report is advertised as Link: <{path}?validate>; rel="describedby" (src/http.rs). Serve it under a relation that is not already taken.

Why

describedby is LDP's description-resource relation. A client following it expects a description auxiliary for the resource and gets a SHACL validation report instead. The two are not interchangeable, and a generic client cannot tell them apart before dereferencing.

It also collides with this pod's own plans: /.aux/{subject}.meta is reserved as the description auxiliary (docs/uri-space.md), so describedby is the relation that resource will want when #63 lands.

How

• Pick a relation that says what the target is. It does not have to be registered: an absolute IRI in this pod's own namespace is honest and costs nothing, and Settle the quadpod.toph.so/ns# namespace before anything else mints into it #73 has to settle that namespace anyway.
• Keep ldp:constrainedBy where it is: pointing at the shape on a refusal is what LDP 4.2.1.6 asks for, and that part is correct today.