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>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.6.2",
+  "version": "2.6.3",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "scripts": {
@@ -32,6 +32,7 @@
     "test:ai-workflow-validation": "node dist/scripts/test-ai-workflow-validation.js",
     "test:mcp-tools": "node dist/scripts/test-mcp-tools.js",
     "test:n8n-manager": "node dist/scripts/test-n8n-manager-integration.js",
+    "test:n8n-validate-workflow": "node dist/scripts/test-n8n-validate-workflow.js",
     "test:typeversion-validation": "node dist/scripts/test-typeversion-validation.js",
     "db:rebuild": "node dist/scripts/rebuild-database.js",
     "db:init": "node -e \"new (require('./dist/services/sqlite-storage-service').SQLiteStorageService)(); console.log('Database initialized')\"",