fix: comprehensive error handling and node-level properties validation (fixes #26)

Root cause: AI agents were placing error handling properties inside `parameters` instead of at node level

Major changes:
- Enhanced workflow validator to check for ALL node-level properties (expanded from 6 to 11)
- Added validation for onError property values and deprecation warnings for continueOnFail
- Updated all examples to use modern error handling (onError instead of continueOnFail)
- Added comprehensive node-level properties documentation in tools_documentation
- Enhanced MCP tool documentation for n8n_create_workflow and n8n_update_partial_workflow
- Added test script demonstrating correct node-level property usage

Node-level properties now validated:
- credentials, disabled, notes, notesInFlow, executeOnce
- onError, retryOnFail, maxTries, waitBetweenTries, alwaysOutputData
- continueOnFail (deprecated)

Validation improvements:
- Detects misplaced properties and provides clear fix examples
- Shows complete node structure when properties are incorrectly placed
- Type validation for all node-level boolean and string properties
- Smart error messages with correct placement guidance

🤖 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": "2.7.10",
+  "version": "2.7.11",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "bin": {
@@ -36,6 +36,7 @@
     "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",
+    "test:error-handling": "node dist/scripts/test-error-handling-validation.js",
     "test:workflow-diff": "node dist/scripts/test-workflow-diff.js",
     "test:transactional-diff": "node dist/scripts/test-transactional-diff.js",
     "test:tools-documentation": "node dist/scripts/test-tools-documentation.js",