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/auto-retry-signal.ts

@@ -0,0 +1,32 @@
+export interface AutoRetrySignal {
+  signal: string
+}
+
+const AUTO_RETRY_PATTERNS: Array<(combined: string) => boolean> = [
+  (combined) => /retrying\s+in/i.test(combined),
+  (combined) =>
+    /(?:too\s+many\s+requests|quota\s+will\s+reset\s+after|quota\s*exceeded|usage\s+limit|rate\s+limit|limit\s+reached|all\s+credentials\s+for\s+model|cool(?:ing)?\s*down|exhausted\s+your\s+capacity)/i.test(combined),
+]
+
+export function extractAutoRetrySignal(info: Record<string, unknown> | undefined): AutoRetrySignal | undefined {
+  if (!info) return undefined
+
+  const candidates: string[] = []
+
+  const directStatus = info.status
+  if (typeof directStatus === "string") candidates.push(directStatus)
+
+  const summary = info.summary
+  if (typeof summary === "string") candidates.push(summary)
+
+  const message = info.message
+  if (typeof message === "string") candidates.push(message)
+
+  const details = info.details
+  if (typeof details === "string") candidates.push(details)
+
+  const combined = candidates.join("\n")
+  if (!combined) return undefined
+
+  return AUTO_RETRY_PATTERNS.some((test) => test(combined)) ? { signal: combined } : undefined
+}