fix(runtime-fallback): match Volcano Engine 'exceeded the usage quota' errors

Volcano Engine sends quota exceeded errors with the words in reverse
order: 'You have exceeded the 5-hour usage quota'. The existing
patterns required 'quota' to precede 'exceeded', so they never matched.

- Add /exceeded.*quota/i and /usage.?quota/i to RETRYABLE_ERROR_PATTERNS
- Add exceeded.*quota and usage\s*quota to AUTO_RETRY_PATTERNS
- Add regression tests for both detection paths

Fixes: runtime-fallback not triggering on Volcano Engine quota errors

src/hooks/runtime-fallback/quota-error-classifier.regression.test.ts

@@ -56,4 +56,19 @@ describe("runtime-fallback quota error regressions", () => {
     // quota errors trigger fallback to next configured model
     expect(retryable).toBe(true)
   })
+
+  test("classifies Volcano Engine 'exceeded the usage quota' as retryable", () => {
+    //#given
+    const error = {
+      name: "SessionRetry",
+      message: "You have exceeded the 5-hour usage quota. It will reset at 2026-05-11 01:20:12 +0800 CST. We recommend using a different model.",
+    }
+
+    //#when
+    const retryable = isRetryableError(error, [429, 500, 502, 503, 504])
+
+    //#then
+    // Volcano Engine quota errors trigger fallback to the next model
+    expect(retryable).toBe(true)
+  })
 })