A crew run paused for credit or a rate limit gives up its slot and says why and when it resumes #11564

Part of #11541. Two runs paused about 17 minutes (run paused … until=00:52, src/crew/dispatch.ts) held a 1-slot forge's only slot, so the builder could not answer a review.

Done looks like:

• [ ] The run paused log line names its cause (credit, rate limit, …).
• [ ] A paused run does not count against the forge's concurrency; another queued run (a review follow-up) can start while it waits.
• [ ] The person sees the pause on the run's card in plain words with the time it resumes.
• [ ] A test with concurrency 1: run A paused until later, run B queued → B starts now; A's line names its cause.