A conversation turn that hits a rate limit rests the account that served it, as a run does #8200

Follow-up of #7651 (asked in the review of #8011). A conversation turn (src/crew/conversation.ts) picks a subscription with pickSubscription, but when the model answers that the account is rate-limited, the turn only ends failed with "I could not answer that just now." The run path (src/crew/runner.ts, around restSubscription) rests the account until its window resets and notes the limit for the account's standing; the conversation path should do the same.

Done when:

• [ ] A turn whose result is a rate limit calls noteLimit and restSubscription with resumeAt/limitOf of the result, as a run does
• [ ] The person sees one line saying the account is resting and until when (no raw provider text)
• [ ] The next message is resting while that account rests and no other can serve, and starts normally once it wakes or another grant is awake
• [ ] A test with a stub claude that answers rate-limited proves the rest, the line, and the refusal; it fails without the code

Files: src/crew/conversation.ts, test/conversation-turn.test.ts

The code this issue extends, src/crew/conversation.ts from pull #8011, isn't on main or on this branch, so there is nothing here to change.

DECLINED: src/crew/conversation.ts and test/conversation-turn.test.ts don't exist on main or on this branch. They are part of pull #8011, which is still open and unmerged. The rate-limit handling this issue asks for builds on that file's say() turn runner. I can't add it without inventing the file, and doing that would collide with #8011. Re-queue this issue once #8011 lands, or stack it on #8011's branch.

Parked by the crew: the run ended without a pull: no changes pushed: The code this issue extends, src/crew/conversation.ts from pull #8011, isn't on main or on this branch, so there is nothing here to change.

Parked by the crew: the run ended without a pull: declined: src/crew/conversation.ts and test/conversation-turn.test.ts don't exist on main or on this branch. They belong to pull #8011, which is still open and unmerged. The rate-limit handling this issue

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the run ended without a pull: no changes pushed: The code this issue extends, src/crew/conversation.ts from pull #8011, isn't on main or on this branch, so there is nothing here to change
2. the run ended without a pull: declined: src/crew/conversation.ts and test/conversation-turn.test.ts don't exist on main or on this branch. They belong to pull #8011, which is still open and unmerged. The rate-limit handling this issue

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Replaced by #8212. Both tries stopped because src/crew/conversation.ts only exists in pull #8011 (#7651), not on main. #8212 asks for the same thing but waits on #7651, so a builder only gets it once the code it extends has landed.