feat(concord): show staff why a room decision was refused or is waiting, and review the room moderation experience hands-on #24

armada-discord-bridge#1 is getting a fix for ban and unban decisions about the same member landing out of order. Depending on which option lands, the bridge will refuse a decision while an earlier one is in flight (409 member_decision_in_progress), refuse a Retry of an older decision once a newer one exists (409 member_decision_superseded), and report new status fields (supersededBy or waitingBehind). Coop's server/routes/concord/service.ts turns any non-200/202 into "Room moderation delivery unavailable" and drops the body, and its status parser drops fields it doesn't read, so staff won't see any of this yet.

To do:

• Show staff why a room decision was refused or is waiting, using the bridge's error codes and status fields from whichever ordering fix lands in armada-discord-bridge#1, and hide Retry where it can't succeed.
• Hands-on: build Coop locally and work through the room moderation flow as staff (report, decide, retry, unban, expiry). Write up what the experience shows and what should change.
• Review Coop's actions overall.

Relates to #23 and divinevideo/armada-discord-bridge#1.