fix: cleanup stale references and update tests after tool removal

- Remove handleListAvailableTools dead code from handlers-n8n-manager.ts
- Update error messages to reference n8n_health_check(mode="diagnostic") instead of n8n_diagnostic
- Update tool counts in diagnostic messages (14 doc tools, 31 total)
- Fix error-handling.test.ts to use valid tools (search_nodes, tools_documentation)
- Remove obsolete list-tools.test.ts integration tests
- Remove unused ListToolsResponse type from response-types.ts
- Update tools.ts QUICK REFERENCE to remove list_nodes references
- Update tools-documentation.ts to remove references to removed tools
- Update tool-docs files to remove stale relatedTools references
- Fix tools.test.ts to not test removed tools (list_nodes, list_ai_tools, etc.)
- Fix parameter-validation.test.ts to not test removed tools
- Update handlers-n8n-manager.test.ts error message expectations

All 399 MCP unit tests now pass.

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

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

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

tests/unit/mcp/handlers-n8n-manager.test.ts

@@ -1031,7 +1031,7 @@ describe('handlers-n8n-manager', () => {
             '1. Verify n8n instance is running',
             '2. Check N8N_API_URL is correct',
             '3. Verify N8N_API_KEY has proper permissions',
-            '4. Run n8n_diagnostic for detailed analysis',
+            '4. Run n8n_health_check with mode="diagnostic" for detailed analysis',
           ],
         },
       });