feat: implement Phase 2 validation improvements

Phase 2 Professional Validation Features:

1. Validation Profiles:
   - minimal: Only required fields
   - runtime: Critical errors + security warnings
   - ai-friendly: Balanced (default)
   - strict: All checks + best practices

2. New Node Validators:
   - Webhook: Path validation, response modes, auth warnings
   - PostgreSQL: SQL injection detection, query safety
   - MySQL: Similar to Postgres with MySQL-specific checks

3. New Tools:
   - validate_node_minimal: Lightning-fast required field checking
   - Updated validate_node_operation with profile support

4. SQL Safety Features:
   - Detects template expressions vulnerable to injection
   - Warns about DELETE/UPDATE without WHERE
   - Catches dangerous operations (DROP, TRUNCATE)
   - Suggests parameterized queries

5. Enhanced Coverage:
   - Now supports 7+ major nodes with specific validators
   - Flexible validation based on use case
   - Professional-grade safety checks

This completes the major validation system overhaul from the original plan.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

src/mcp/tools-update.ts

@@ -181,7 +181,7 @@ export const n8nDocumentationToolsFinal: ToolDefinition[] = [
   },
   {
     name: 'validate_node_operation',
-    description: `Verify your node configuration is correct before using it. Checks: required fields are present, values are valid types/formats, operation-specific rules are met. Returns specific errors with fixes (e.g., "Channel required to send Slack message - add channel: '#general'"), warnings about common issues, working examples when errors found, and suggested next steps. Smart validation that only checks properties relevant to your selected operation/action. Essential for Slack, Google Sheets, MongoDB, OpenAI nodes.`,
+    description: `Verify your node configuration is correct before using it. Checks: required fields are present, values are valid types/formats, operation-specific rules are met. Returns specific errors with fixes (e.g., "Channel required to send Slack message - add channel: '#general'"), warnings about common issues, working examples when errors found, and suggested next steps. Smart validation that only checks properties relevant to your selected operation/action. Essential for Slack, Google Sheets, MongoDB, OpenAI nodes. Supports validation profiles for different use cases.`,
     inputSchema: {
       type: 'object',
       properties: {
@@ -193,6 +193,30 @@ export const n8nDocumentationToolsFinal: ToolDefinition[] = [
           type: 'object',
           description: 'Your node configuration. Must include operation fields (resource/operation/action) if the node has multiple operations.',
         },
+        profile: {
+          type: 'string',
+          enum: ['strict', 'runtime', 'ai-friendly', 'minimal'],
+          description: 'Validation profile: minimal (only required fields), runtime (critical errors only), ai-friendly (balanced - default), strict (all checks including best practices)',
+          default: 'ai-friendly',
+        },
+      },
+      required: ['nodeType', 'config'],
+    },
+  },
+  {
+    name: 'validate_node_minimal',
+    description: `Quick validation that ONLY checks for missing required fields. Returns just the list of required fields that are missing. Fastest validation option - use when you only need to know if required fields are present. No warnings, no suggestions, no examples - just missing required fields.`,
+    inputSchema: {
+      type: 'object',
+      properties: {
+        nodeType: {
+          type: 'string',
+          description: 'The node type to validate (e.g., "nodes-base.slack")',
+        },
+        config: {
+          type: 'object',
+          description: 'The node configuration to check',
+        },
       },
       required: ['nodeType', 'config'],
     },