fix: 修复额度耗尽错误展示

问题：Token balance exhausted 被作为原始助手气泡展示，且额度确认可能跨会话复用。

修复：区分绝对余额与滚动额度，绑定当前会话失败 key，并补充真实消息结构与双会话回归测试。

shared/opencode-error-kind.ts

@@ -1,18 +1,23 @@
 export type OpencodeErrorKind = 'quota_exhausted' | 'authentication_invalid';
 
+export function isOpencodeTokenBalanceExhausted(message: string | null | undefined): boolean {
+  const normalized = message?.trim().toLowerCase() ?? '';
+  return normalized.includes('token_balance_exhausted')
+    || normalized.includes('token balance exhausted')
+    || normalized.includes('balance exhausted');
+}
+
 export function getOpencodeErrorKind(message: string | null | undefined): OpencodeErrorKind | null {
   const normalized = message?.trim().toLowerCase() ?? '';
   if (!normalized) return null;
   if (
-    normalized.includes('user quota is not enough')
+    isOpencodeTokenBalanceExhausted(normalized)
+    || normalized.includes('user quota is not enough')
     || normalized.includes('quota is not enough')
     || normalized.includes('quota not enough')
     || normalized.includes('insufficient quota')
     || normalized.includes('quota exhausted')
     || normalized.includes('quota exceeded')
-    || normalized.includes('token_balance_exhausted')
-    || normalized.includes('token balance exhausted')
-    || normalized.includes('balance exhausted')
     || normalized.includes('rolling 5-hour window')
     || normalized.includes('额度不足')
   ) {