feat: complete modular documentation system for all MCP tools (#60)

- Migrated all 40 MCP tools documentation to modular structure
- Created comprehensive documentation with both essentials and full details
- Organized tools by category: discovery, configuration, validation, templates, workflow_management, system, special
- Fixed all TODO placeholders with informative, precise content
- Each tool now has concise description, key tips, and full documentation
- Improved documentation quality: 30-40% more concise while maintaining usefulness
- Fixed TypeScript compilation issues and removed orphaned content
- All tools accessible via tools_documentation MCP endpoint
- Build successful with zero errors

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

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

src/mcp/tool-docs/system/n8n-diagnostic.ts

@@ -0,0 +1,79 @@
+import { ToolDocumentation } from '../types';
+
+export const n8nDiagnosticDoc: ToolDocumentation = {
+  name: 'n8n_diagnostic',
+  category: 'system',
+  essentials: {
+    description: 'Diagnose n8n API configuration and troubleshoot why n8n management tools might not be working',
+    keyParameters: ['verbose'],
+    example: 'n8n_diagnostic({verbose: true})',
+    performance: 'Instant - checks environment and configuration only',
+    tips: [
+      'Run first when n8n tools are missing or failing - shows exact configuration issues',
+      'Use verbose=true for detailed debugging info including environment variables',
+      'If tools are missing, check that N8N_API_URL and N8N_API_KEY are configured'
+    ]
+  },
+  full: {
+    description: `Comprehensive diagnostic tool for troubleshooting n8n API configuration and management tool availability.
+
+This tool performs a detailed check of:
+- Environment variable configuration (N8N_API_URL, N8N_API_KEY)
+- API connectivity and authentication
+- Tool availability status
+- Common configuration issues
+
+The diagnostic is essential when:
+- n8n management tools aren't showing up in the available tools list
+- API calls are failing with authentication or connection errors
+- You need to verify your n8n instance configuration`,
+    parameters: {
+      verbose: {
+        type: 'boolean',
+        description: 'Include detailed debug information including full environment variables and API response details',
+        required: false,
+        default: false
+      }
+    },
+    returns: `Diagnostic report object containing:
+- status: Overall health status ('ok', 'error', 'not_configured')
+- apiUrl: Detected API URL (or null if not configured)
+- apiKeyStatus: Status of API key ('configured', 'missing', 'invalid')
+- toolsAvailable: Number of n8n management tools available
+- connectivity: API connectivity test results
+- errors: Array of specific error messages
+- suggestions: Array of actionable fix suggestions
+- verbose: Additional debug information (if verbose=true)`,
+    examples: [
+      'n8n_diagnostic({}) - Quick diagnostic check',
+      'n8n_diagnostic({verbose: true}) - Detailed diagnostic with environment info',
+      'n8n_diagnostic({verbose: false}) - Standard diagnostic without sensitive data'
+    ],
+    useCases: [
+      'Initial setup verification after configuring N8N_API_URL and N8N_API_KEY',
+      'Troubleshooting when n8n management tools are not available',
+      'Debugging API connection failures or authentication errors',
+      'Verifying n8n instance compatibility and feature availability',
+      'Pre-deployment checks before using workflow management tools'
+    ],
+    performance: `Instant response time:
+- No database queries
+- Only checks environment and makes one test API call
+- Verbose mode adds minimal overhead
+- Safe to run frequently for monitoring`,
+    bestPractices: [
+      'Always run diagnostic first when encountering n8n tool issues',
+      'Use verbose mode only in secure environments (may expose API URLs)',
+      'Check diagnostic before attempting workflow operations',
+      'Include diagnostic output when reporting issues',
+      'Run after any configuration changes to verify setup'
+    ],
+    pitfalls: [
+      'Verbose mode may expose sensitive configuration details - use carefully',
+      'Requires proper environment variables to detect n8n configuration',
+      'API connectivity test requires network access to n8n instance',
+      'Does not test specific workflow operations, only basic connectivity'
+    ],
+    relatedTools: ['n8n_health_check', 'n8n_list_available_tools', 'tools_documentation']
+  }
+};