fix(oauth+errors): OAuth silent refresh, quota STOP patterns, compaction loop cap

Bug fixes:
1. OAuth token refresh (#3149): buildHttpRequestInit() now attempts silent refresh
   via refresh_token before triggering full browser re-auth. Added refresh() method
   to McpOAuthProvider. Includes test isolation fix for discovery mock.

2. Quota error STOP (#3126): Added STOP_MESSAGE_PATTERNS in model-error-classifier
   that take precedence over RETRYABLE_MESSAGE_PATTERNS. Message-only quota errors
   now non-retryable. Runtime-fallback: quota_exceeded with 'retrying in' signal
   still triggers fallback (provider-managed auto-retry). Restored removed patterns.

3. Compaction loop (#3127): MAX_RECOVERY_ATTEMPTS=3 cap + additional suppression
   guard from opencode session in degradation monitor.

Also: refactored extractAutoRetrySignal to auto-retry-signal.ts, new regression
tests for quota classifier and compaction degradation monitor.

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

@@ -0,0 +1,56 @@
+import { describe, expect, test } from "bun:test"
+
+import { classifyErrorType, isRetryableError } from "./error-classifier"
+
+describe("runtime-fallback quota error regressions", () => {
+  test("classifies subscription quota errors as quota_exceeded and stops retry", () => {
+    //#given
+    const error = {
+      name: "AI_APICallError",
+      message: "Subscription quota exceeded. You can continue using free models.",
+    }
+
+    //#when
+    const errorType = classifyErrorType(error)
+    const retryable = isRetryableError(error, [429, 500, 502, 503, 504])
+
+    //#then
+    expect(errorType).toBe("quota_exceeded")
+    expect(retryable).toBe(false)
+  })
+
+  test("treats HTTP 402 payment required as non-retryable", () => {
+    //#given
+    const error = { statusCode: 402, message: "Payment Required" }
+
+    //#when
+    const retryable = isRetryableError(error, [429, 500, 502, 503, 504])
+
+    //#then
+    expect(retryable).toBe(false)
+  })
+
+  test("keeps HTTP 429 rate limit retryable", () => {
+    //#given
+    const error = { statusCode: 429, message: "Too Many Requests: rate limit reached" }
+
+    //#when
+    const retryable = isRetryableError(error, [429, 500, 502, 503, 504])
+
+    //#then
+    expect(retryable).toBe(true)
+  })
+
+  test("classifies quota error names as quota_exceeded without retry", () => {
+    //#given
+    const error = { name: "QuotaExceededError", message: "Request failed." }
+
+    //#when
+    const errorType = classifyErrorType(error)
+    const retryable = isRetryableError(error, [429, 500, 502, 503, 504])
+
+    //#then
+    expect(errorType).toBe("quota_exceeded")
+    expect(retryable).toBe(false)
+  })
+})