fix(pr-bot): fail fast when the review model's budget is spent

Claude Code answers an exhausted model budget INSIDE the turn ("You've
reached your Fable limit. Run /usage-credits to continue or switch models
with /model.") and then sits there with nothing to write. The reviewer never
produces a report, so `runTurn` waited out its full 40-minute deadline and
reported a bare "timed out after 40 min without a report", which reads as a
hung reviewer rather than an account that needs attention.

Measured on 2026-09-08: #388, #393, #394 and #377 each lost 40 minutes this
way, and because every attempt counted, all four reached MAX_AUTO_RETRIES and
would NOT have been picked up again once the budget returned. One spent
afternoon quietly took the whole queue out of service.

`findModelLimitNotice()` reads the notice off the pane and `runTurn` returns
a new `limit` outcome instead of waiting. It is consulted in exactly two
places, both of which mean "the turn produced nothing": on a stop where
`isDone()` is still false, and on each timed-out wait slice. A review that
merely discusses usage limits in its own findings therefore cannot be
mistaken for one that hit the wall, and the pattern matches neither the model
name nor a straight apostrophe, since the pane renders a typographic one and
every model prints the same sentence.

A spent budget is an account condition, not a bad PR, so it no longer spends
the per-head retry budget: the queue resumes by itself when the budget does.
Telegram now names the cause and the file to change.

Tests use the pane captured verbatim off the run that lost the 40 minutes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/pr-bot.md

@@ -90,7 +90,7 @@ has to be copied; set them here to use a different bot.
 | `PR_BOT_POLL_INTERVAL` | `600` | Seconds between GitHub polls (minimum 60). |
 | `PR_BOT_MAIN_CHECKOUT` | the repo this script is in | The repository the clones share objects with and fetch from. |
 | `PR_BOT_DATA_DIR` | `~/.codeman/pr-bot` | State, briefs, reports, clones. |
-| `PR_BOT_MODEL` | unset (the session default) | Codeman `modelOverride` for the review sessions, e.g. `claude-fable-5-1`. |
+| `PR_BOT_MODEL` | unset (the session default) | Codeman `modelOverride` for the review sessions, e.g. `opus[1m]`. ⚠️ Pick a model whose budget can absorb a re-review of every open PR on every head commit: when it runs out, Claude Code answers the limit **inside the turn** and the reviewer has nothing to write. The bot now names that failure in seconds (`findModelLimitNotice`) instead of burning the whole `PR_BOT_REVIEW_TIMEOUT`, and a limit does not spend the per-head retry budget, so the queue resumes by itself once the budget does. |
 | `PR_BOT_EFFORT` | unset | Codeman `effort` for the review sessions. |
 | `PR_BOT_REVIEW_TIMEOUT` | `40` | Minutes before a review is abandoned. |
 | `PR_BOT_FOLLOWUP_TIMEOUT` | `20` | Minutes before a follow-up is abandoned. |