The /__forge/ door says who of the crew is working on this app or preview now, as the pill does #7853

Intent: on an app whose CSP refuses the pill, the door at /__forge/ is the only way back to the forge, and it should answer "who is working on it" just as the pill's crew line does.

Done when:

• [ ] DoorFacts in src/apps/door.ts gains an optional crew line. The door handler in src/apps/proxy.ts fills it from the same crewNow(...) call /__forge/crew makes, with the same viewer, so a run the viewer may not see is never named.
• [ ] When a crew run is working, the door shows "<who> is working on this" as a link to that run on the forge, using the same words and target as the pill. When none is working, nothing is shown, and the page is otherwise byte-for-byte what it is today.
• [ ] Text is escaped with escapeAttr, and the URL is built with new URL on forgeUrl. The CSP is unchanged: still no script.
• [ ] A test in test/apps-door.test.ts fails without the change. It covers a running agent run on the app (named and linked), none running (no line), and a run on a sealed issue the viewer may not see (not named).

Files: src/apps/door.ts, src/apps/proxy.ts, test/apps-door.test.ts Risks: #6438 also edits pullsHtml in src/apps/door.ts. Keep this change to its own function so the two merge cleanly.