Why a principal was refused, typed.This replaces the stringly-typed enriched 403, which carried access_mode: String and whose
tests asserted a sentinel "join_request" that was never a real mode
(temper-services/src/error.rs:299,377 — verified: the live domain is open/invite_only).Spec §12: "Every illegal cell asserts a reason, not just a refusal. The point of refusing at
the act is that the actor learns why; a test that only checks 'not admitted' would pass on a
silent denial."
{
"kind": "no_standing"
}