fix(retry): recognize ZhiPu 1302 rate-limit error for retry

ZhiPu API returns code 1302 with Chinese text "速率限制" instead of
standard HTTP 429 + "rate limit", causing the retry engine to treat
it as non-transient and fail immediately.

nanobot/providers/base.py

@@ -108,6 +108,7 @@ class LLMProvider(ABC):
         "connection",
         "server error",
         "temporarily unavailable",
+        "速率限制",
     )
     _RETRYABLE_STATUS_CODES = frozenset({408, 409, 429})
     _TRANSIENT_ERROR_KINDS = frozenset({"timeout", "connection"})
@@ -154,6 +155,7 @@ class LLMProvider(ABC):
         "temporarily unavailable",
         "overloaded",
         "concurrency limit",
+        "速率限制",
     )
 
     _SENTINEL = object()