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/features/skill-mcp-manager/oauth-handler.ts

@@ -44,7 +44,7 @@ export async function buildHttpRequestInit(
     const provider = getOrCreateAuthProvider(authProviders, config.url, config.oauth, createOAuthProvider)
     let tokenData = provider.tokens()
 
-    if (!tokenData || isTokenExpired(tokenData)) {
+    if (!tokenData) {
       try {
         tokenData = await provider.login()
       } catch {
@@ -52,6 +52,20 @@ export async function buildHttpRequestInit(
       }
     }
 
+    if (tokenData && isTokenExpired(tokenData)) {
+      try {
+        tokenData = tokenData.refreshToken
+          ? await provider.refresh(tokenData.refreshToken)
+          : await provider.login()
+      } catch {
+        try {
+          tokenData = await provider.login()
+        } catch {
+          tokenData = null
+        }
+      }
+    }
+
     if (tokenData) {
       headers.Authorization = `Bearer ${tokenData.accessToken}`
     }