Surface failed-turn reason: host.py recovers it from thread_history, dispatch prints it

Real bad-model turn: relay returns 404, codex retries sampling
5 times, turn fails, but app-server's turn/completed event
carries status=failed with NO error and NO text, so worker
never saw any fallbackable signal. The 404 actually lives in
codex's thread_history_1.sqlite (thread_turns.error_json).
host.py Server.run_turn now best-effort recovers that message
(read-only query by thread_id+turn_id, any failure -> None,
never breaks the turn itself), and dispatch CLI prints the
error field (run CLI already printed the full result). Worker
_attempt_error prefers the error field when text is empty, so
a double failure keeps the real reasons, not just status codes.
Tests: host TurnErrorFromHistoryTest (recovery + missing/corrupt
DB -> None), full host + cloud suites pass.

cloud/worker.py

@@ -905,6 +905,14 @@ class Worker:
             parsed = None
         if isinstance(parsed, dict) and parsed.get("text"):
             return str(parsed["text"])
+        # dispatch 输出现在带 error 字段（host.py 从 thread_history
+        # 库里捞回的失败原因，如 404）；text 为空时优先用它，
+        # 否则两次失败的拼接里只剩 host_status=404 这种代号。
+        if isinstance(parsed, dict) and parsed.get("error"):
+            err = parsed["error"]
+            if isinstance(err, dict):
+                err = err.get("message") or str(err)
+            return str(err)[:1000]
         # host.py 崩溃时 stdout 常为空、真正的报错在 stderr（例如
         # “缺少 --repo”、Read-only file system）；只用 stdout 时
         # 最终错误会被写成通用的 host execution failed，排障无从