feat: add n8n_validate_workflow tool (v2.6.3)

- NEW: n8n_validate_workflow tool to validate workflows from n8n instance by ID
- Fetches workflow via API and runs comprehensive validation
- Uses existing WorkflowValidator for consistency
- Supports all validation profiles and options
- Updated start_here tool with new workflow lifecycle info
- Updated README with new tool documentation
- Updated Claude Project Setup instructions

This completes the workflow lifecycle management:
discover → build → validate → deploy → execute → monitor

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

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

src/scripts/test-n8n-validate-workflow.ts

@@ -0,0 +1,113 @@
+#!/usr/bin/env ts-node
+
+/**
+ * Test script for the n8n_validate_workflow tool
+ * 
+ * This script tests the new tool that fetches a workflow from n8n
+ * and validates it using the existing validation logic.
+ */
+
+import { config } from 'dotenv';
+import { handleValidateWorkflow } from '../mcp/handlers-n8n-manager';
+import { NodeRepository } from '../database/node-repository';
+import { createDatabaseAdapter } from '../database/database-adapter';
+import { Logger } from '../utils/logger';
+import * as path from 'path';
+
+// Load environment variables
+config();
+
+const logger = new Logger({ prefix: '[TestN8nValidateWorkflow]' });
+
+async function testN8nValidateWorkflow() {
+  try {
+    // Check if n8n API is configured
+    if (!process.env.N8N_API_URL || !process.env.N8N_API_KEY) {
+      logger.error('N8N_API_URL and N8N_API_KEY must be set in environment variables');
+      process.exit(1);
+    }
+
+    logger.info('n8n API Configuration:', {
+      url: process.env.N8N_API_URL,
+      hasApiKey: !!process.env.N8N_API_KEY
+    });
+
+    // Initialize database
+    const dbPath = path.join(process.cwd(), 'data', 'nodes.db');
+    const db = await createDatabaseAdapter(dbPath);
+    const repository = new NodeRepository(db);
+
+    // Test cases
+    const testCases = [
+      {
+        name: 'Validate existing workflow with all options',
+        args: {
+          id: '1', // Replace with an actual workflow ID from your n8n instance
+          options: {
+            validateNodes: true,
+            validateConnections: true,
+            validateExpressions: true,
+            profile: 'runtime'
+          }
+        }
+      },
+      {
+        name: 'Validate with minimal profile',
+        args: {
+          id: '1', // Replace with an actual workflow ID
+          options: {
+            profile: 'minimal'
+          }
+        }
+      },
+      {
+        name: 'Validate connections only',
+        args: {
+          id: '1', // Replace with an actual workflow ID
+          options: {
+            validateNodes: false,
+            validateConnections: true,
+            validateExpressions: false
+          }
+        }
+      }
+    ];
+
+    // Run test cases
+    for (const testCase of testCases) {
+      logger.info(`\nRunning test: ${testCase.name}`);
+      logger.info('Input:', JSON.stringify(testCase.args, null, 2));
+
+      try {
+        const result = await handleValidateWorkflow(testCase.args, repository);
+        
+        if (result.success) {
+          logger.info('✅ Validation completed successfully');
+          logger.info('Result:', JSON.stringify(result.data, null, 2));
+        } else {
+          logger.error('❌ Validation failed');
+          logger.error('Error:', result.error);
+          if (result.details) {
+            logger.error('Details:', JSON.stringify(result.details, null, 2));
+          }
+        }
+      } catch (error) {
+        logger.error('❌ Test case failed with exception:', error);
+      }
+
+      logger.info('-'.repeat(80));
+    }
+
+    logger.info('\n✅ All tests completed');
+
+  } catch (error) {
+    logger.error('Test script failed:', error);
+    process.exit(1);
+  }
+}
+
+// Run the test
+testN8nValidateWorkflow().catch(error => {
+  logger.error('Unhandled error:', error);
+  process.exit(1);
+});