The review and build briefs say a preview's /__forge/ and pill come from the host forge, so changes to them are judged by test #6356

Later: The repository is FLOW ONLY until the #5930 alarms stay clear for 24 h, and this is not flow work.

Replaces #6100, deferred while the repository is FLOW ONLY. Pull #6255 built it, and its code was judged sound; rebuild from its branch on a fresh main.

Three pulls this month (#5988, #6032, #6078) took change requests for something no preview can show. On an app host, /__forge/* and the injected pill are answered by the forge that hosts the app.

Done:

• [ ] hostDoorRule in src/crew/brief.ts matches a change to src/apps/door.ts, toolbar.ts, feedback.ts or door_pulls.ts, and to proxy.ts only with __forge. Review diffs are matched on their diff --git headers; an issue's text is matched as free text.
• [ ] Such a change makes the reviewer and builder briefs say, in one line, that /__forge/* and the forge pill on a preview come from the host forge: judge them by the request-level tests that come with the change, not by the preview. Every other brief is unchanged.
• [ ] Tests call the production functions (touchesHostDoor, hostDoorFor, builderHostDoor) for door.ts (present), src/web/ only (absent), and a docs-only diff that mentions door.ts (absent).
• [ ] docs/CREW.md says it in one sentence where it describes previews.