Add Chinese context overflow patterns to isContextOverflowError (#22855)

Proxy providers returning Chinese error messages (e.g. Chinese LLM
gateways) use patterns like '上下文过长' or '上下文超出' that are not
matched by the existing English-only patterns in isContextOverflowError.
This prevents auto-compaction from triggering, leaving the session stuck.

Add the most common Chinese proxy patterns:
- 上下文过长 (context too long)
- 上下文超出 (context exceeded)
- 上下文长度超 (context length exceeds)
- 超出最大上下文 (exceeds maximum context)
- 请压缩上下文 (please compress context)

Chinese characters are unaffected by toLowerCase() so check the
original message directly.

Closes #22849

src/agents/pi-embedded-helpers/errors.ts

@@ -81,7 +81,13 @@ export function isContextOverflowError(errorMessage?: string): boolean {
     lower.includes("exceeds the model's maximum context") ||
     (lower.includes("max_tokens") && lower.includes("exceed") && lower.includes("context")) ||
     (lower.includes("input length") && lower.includes("exceed") && lower.includes("context")) ||
-    (lower.includes("413") && lower.includes("too large"))
+    (lower.includes("413") && lower.includes("too large")) ||
+    // Chinese proxy error messages for context overflow
+    errorMessage.includes("上下文过长") ||
+    errorMessage.includes("上下文超出") ||
+    errorMessage.includes("上下文长度超") ||
+    errorMessage.includes("超出最大上下文") ||
+    errorMessage.includes("请压缩上下文")
   );
 }