fix: resolve remaining AI validation integration test failures

- Simplified Calculator and Think tool validators (no toolDescription required - built-in descriptions)
- Fixed trigger counting to exclude respondToWebhook from trigger detection
- Fixed streaming error filters to use correct error code access pattern (details.code || code)

This resolves 9 remaining integration test failures from Phase 2 AI validation implementation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/integration/ai-validation/e2e-validation.test.ts

@@ -219,10 +219,11 @@ describe('Integration: End-to-End AI Workflow Validation', () => {
     expect(errorCodes).toContain('MISSING_CODE'); // Code Tool
 
     // Should also have streaming error
-    const streamingErrors = validationData.errors!.filter(e =>
-      e.code === 'STREAMING_WITH_MAIN_OUTPUT' ||
-      e.code === 'STREAMING_AGENT_HAS_OUTPUT'
-    );
+    const streamingErrors = validationData.errors!.filter(e => {
+      const code = e.details?.code || e.code;
+      return code === 'STREAMING_WITH_MAIN_OUTPUT' ||
+             code === 'STREAMING_AGENT_HAS_OUTPUT';
+    });
     expect(streamingErrors.length).toBeGreaterThan(0);
 
     // Verify error messages are actionable