Messages reach exactly who they name

Steps

1. 1 None Offstage: the manager addresses a thread to Door staff for this event 0:01
2. 2 door Door staff open their inbox on a phone 0:05 ▣

   This staffer was never added to the thread by hand. They hold the role, and the role is who it was addressed to.

3. 3 door Open it 0:07 ▣

   The body, and above it the thing plan 105 added: who this went to.

4. 4 Member A member opens their inbox 0:11 ▣

   Same page, same moment. A member holds no door role, so the briefing is not theirs to read.

5. 5 Member And the URL itself gives nothing away 0:12 ▣

   404, not 403. The existence of a thread is itself private, so the page must not confirm that this one is real.

6. 6 manager The manager's console, on a desktop 0:18 ▣

   Staff-wide read is a product decision, so the page is supposed to say that rather than look like a personal inbox holding other people's mail.