feat(serving): propose a quoted path from committed input, grant nothing

Build the substrate both authorization arms of the quoted-path fork share. A path is read from a committed user input only, never from an outbound message, raw terminal bytes or a mid-turn span, and is bound to that input's identity, its exact payload and the receiving endpoint's incarnation. The proposal names the entry a grant would create — the one receiving endpoint as audience, twenty-four hours, one proposal per path — and stops there: the authorization arm is the operator's decision, so every proposal refuses at a named seam and nothing is registered or served. Replaying an input reproduces its proposal rather than asking again, and a later incarnation inherits none. Register the substrate requirement with its stages and the authorization requirement with none.

Co-authored by: todlando