DL-383

A channel member refused by an OWNER_ONLY post policy (a post or a pinned-board change) gets PermissionDenied naming the channel as owner-only; a non-member keeps NotFound. A member can already read the channel, so the distinct code leaks nothing. Amends DL-136’s “same in-band error a non-member gets” clause

Status: Active (Matt, 2026-09-30)

Record: ../../agent/compass-manager-comms-substrate/design.md#a2–rig-1722-coordination-channel–a-channel-level-post_policy–mandatory_subscription-auto-provisioned-from-tree-edges