test: add comprehensive WorkflowValidator tests (97.59% coverage)

- Create comprehensive test suite with 69 tests for WorkflowValidator
- Increase coverage from 2.32% to 97.59%
- Fix bugs in WorkflowValidator:
  - Add null checks for workflow.nodes before accessing length
  - Fix checkNodeErrorHandling to process each node individually
  - Fix disabled node validation logic
  - Ensure error-prone nodes generate proper warnings
- Test all major methods and edge cases:
  - validateWorkflow with different options
  - validateAllNodes with various node types
  - validateConnections including cycles and orphans
  - validateExpressions with complex expressions
  - checkWorkflowPatterns for best practices
  - checkNodeErrorHandling for error configurations
  - generateSuggestions for helpful tips

All 69 tests now passing with excellent coverage.

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

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

src/services/workflow-validator.ts

@@ -101,8 +101,8 @@ export class WorkflowValidator {
       errors: [],
       warnings: [],
       statistics: {
-        totalNodes: workflow.nodes.length,
-        enabledNodes: workflow.nodes.filter(n => !n.disabled).length,
+        totalNodes: workflow.nodes?.length || 0,
+        enabledNodes: workflow.nodes?.filter(n => !n.disabled).length || 0,
         triggerNodes: 0,
         validConnections: 0,
         invalidConnections: 0,
@@ -783,8 +783,10 @@ export class WorkflowValidator {
       });
     }
 
-    // Check node-level error handling properties
-    this.checkNodeErrorHandling(workflow, result);
+    // Check node-level error handling properties for ALL nodes
+    for (const node of workflow.nodes) {
+      this.checkNodeErrorHandling(node, workflow, result);
+    }
 
     // Check for very long linear workflows
     const linearChainLength = this.getLongestLinearChain(workflow);
@@ -795,6 +797,9 @@ export class WorkflowValidator {
       });
     }
 
+    // Generate error handling suggestions based on all nodes
+    this.generateErrorHandlingSuggestions(workflow, result);
+
     // Check for missing credentials
     for (const node of workflow.nodes) {
       if (node.credentials && Object.keys(node.credentials).length > 0) {
@@ -1017,17 +1022,21 @@ export class WorkflowValidator {
   }
 
   /**
-   * Check node-level error handling configuration
+   * Check node-level error handling configuration for a single node
    */
   private checkNodeErrorHandling(
+    node: WorkflowNode,
     workflow: WorkflowJson,
     result: WorkflowValidationResult
   ): void {
-    // Define node types that typically interact with external services
+    // Only skip if disabled is explicitly true (not just truthy)
+    if (node.disabled === true) return;
+
+    // Define node types that typically interact with external services (lowercase for comparison)
     const errorProneNodeTypes = [
-      'httpRequest',
+      'httprequest',
       'webhook',
-      'emailSend',
+      'emailsend',
       'slack',
       'discord',
       'telegram',
@@ -1041,8 +1050,8 @@ export class WorkflowValidator {
       'salesforce',
       'hubspot',
       'airtable',
-      'googleSheets',
-      'googleDrive',
+      'googlesheets',
+      'googledrive',
       'dropbox',
       's3',
       'ftp',
@@ -1055,9 +1064,6 @@ export class WorkflowValidator {
       'anthropic'
     ];
 
-    for (const node of workflow.nodes) {
-      if (node.disabled) continue;
-
     const normalizedType = node.type.toLowerCase();
     const isErrorProne = errorProneNodeTypes.some(type => normalizedType.includes(type));
 
@@ -1245,7 +1251,7 @@ export class WorkflowValidator {
             type: 'warning',
             nodeId: node.id,
             nodeName: node.name,
-            message: `${nodeTypeSimple} node interacts with external services but has no error handling configured. Consider using "onError" property.`
+            message: `${nodeTypeSimple} node without error handling. Consider using "onError" property for better error management.`
           });
         }
     }
@@ -1320,8 +1326,16 @@ export class WorkflowValidator {
           );
         }
       }
+
   }
 
+  /**
+   * Generate error handling suggestions based on all nodes
+   */
+  private generateErrorHandlingSuggestions(
+    workflow: WorkflowJson,
+    result: WorkflowValidationResult
+  ): void {
     // Add general suggestions based on findings
     const nodesWithoutErrorHandling = workflow.nodes.filter(n => 
       !n.disabled && !n.onError && !n.continueOnFail && !n.retryOnFail