fix(runtime-fallback): also classify Volcano Engine errors as quota_exceeded

- Add /exceeded.*quota/i and /usage\s*quota/i to classifyErrorType quota block
- Align /usage.?quota/i -> /usage\s*quota/i in RETRYABLE_ERROR_PATTERNS for consistency
- Strengthen auto-retry-signal test assertion
- Add classifyErrorType assertion to Volcano Engine regression test

Ensures Volcano Engine errors are both retryable AND logged as
errorType: quota_exceeded.

src/hooks/runtime-fallback/error-classifier.ts

@@ -126,6 +126,8 @@ export function classifyErrorType(error: unknown): string | undefined {
     errorName?.includes("insufficientquota") ||
     errorName?.includes("billingerror") ||
     /quota.?exceeded/i.test(message) ||
+    /exceeded.*quota/i.test(message) ||
+    /usage\s*quota/i.test(message) ||
     /subscription.*quota/i.test(message) ||
     /insufficient.?(?:quota|balance|funds?)/i.test(message) ||
     /billing.?(?:hard.?)?limit/i.test(message) ||