fix(p0): remove incorrect node type normalization before n8n API calls

## Bug Description
handleCreateWorkflow and handleUpdateFullWorkflow were incorrectly
normalizing node types from FULL form (n8n-nodes-base.webhook) to
SHORT form (nodes-base.webhook) before validation and API calls.

This caused 100% failure rate for workflow creation because:
- n8n API requires FULL form (n8n-nodes-base.*)
- Database stores SHORT form (nodes-base.*)
- NodeTypeNormalizer converts TO SHORT form (for database)
- But was being used BEFORE API calls (incorrect)

## Root Cause
NodeTypeNormalizer was designed for database lookups but was
incorrectly applied to API operations. The method name
`normalizeToFullForm()` is misleading - it actually normalizes
TO SHORT form.

## Changes
1. handlers-n8n-manager.ts:
   - Removed NodeTypeNormalizer.normalizeWorkflowNodeTypes() from
     handleCreateWorkflow (line 288)
   - Removed normalization from handleUpdateFullWorkflow (line 544-557)
   - Added proactive SHORT form detection with helpful errors
   - Added comments explaining n8n API expects FULL form

2. node-type-normalizer.ts:
   - Added prominent WARNING about not using before API calls
   - Added examples showing CORRECT vs INCORRECT usage
   - Clarified this is FOR DATABASE OPERATIONS ONLY

3. handlers-n8n-manager.test.ts:
   - Fixed test to expect FULL form (not SHORT) sent to API
   - Removed incorrect expectedNormalizedInput assertion

4. NEW: workflow-creation-node-type-format.test.ts:
   - 7 integration tests with real validation (unmocked)
   - Tests FULL form acceptance, SHORT form rejection
   - Tests real-world workflows (webhook, schedule trigger)
   - Regression test to prevent bug reintroduction

## Verification
Before fix:
❌ Manual Trigger → Set: FAILED
❌ Webhook → HTTP Request: FAILED
Failure rate: 100%

After fix:
✅ Manual Trigger → Set: SUCCESS (ID: kTAaDZwdpzj8gqzM)
✅ Webhook → HTTP Request: SUCCESS (ID: aPtQUb54uuHIqX52)
✅ All 39 tests passing (32 unit + 7 integration)
Success rate: 100%

## Impact
- Fixes: Complete blocking bug preventing all workflow creation
- Risk: Zero (removing buggy behavior)
- Breaking: None (external API unchanged)

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

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

src/mcp/handlers-n8n-manager.ts

@@ -284,14 +284,37 @@ export async function handleCreateWorkflow(args: unknown, context?: InstanceCont
     const client = ensureApiConfigured(context);
     const input = createWorkflowSchema.parse(args);
 
-    // Normalize all node types before validation
-    const normalizedInput = NodeTypeNormalizer.normalizeWorkflowNodeTypes(input);
+    // Proactively detect SHORT form node types (common mistake)
+    const shortFormErrors: string[] = [];
+    input.nodes?.forEach((node: any, index: number) => {
+      if (node.type?.startsWith('nodes-base.') || node.type?.startsWith('nodes-langchain.')) {
+        const fullForm = node.type.startsWith('nodes-base.')
+          ? node.type.replace('nodes-base.', 'n8n-nodes-base.')
+          : node.type.replace('nodes-langchain.', '@n8n/n8n-nodes-langchain.');
+        shortFormErrors.push(
+          `Node ${index} ("${node.name}") uses SHORT form "${node.type}". ` +
+          `The n8n API requires FULL form. Change to "${fullForm}"`
+        );
+      }
+    });
 
-    // Validate workflow structure
-    const errors = validateWorkflowStructure(normalizedInput);
+    if (shortFormErrors.length > 0) {
+      telemetry.trackWorkflowCreation(input, false);
+      return {
+        success: false,
+        error: 'Node type format error: n8n API requires FULL form node types',
+        details: {
+          errors: shortFormErrors,
+          hint: 'Use n8n-nodes-base.* instead of nodes-base.* for standard nodes'
+        }
+      };
+    }
+
+    // Validate workflow structure (n8n API expects FULL form: n8n-nodes-base.*)
+    const errors = validateWorkflowStructure(input);
     if (errors.length > 0) {
       // Track validation failure
-      telemetry.trackWorkflowCreation(normalizedInput, false);
+      telemetry.trackWorkflowCreation(input, false);
 
       return {
         success: false,
@@ -300,8 +323,8 @@ export async function handleCreateWorkflow(args: unknown, context?: InstanceCont
       };
     }
 
-    // Create workflow with normalized node types
-    const workflow = await client.createWorkflow(normalizedInput);
+    // Create workflow (n8n API expects node types in FULL form)
+    const workflow = await client.createWorkflow(input);
 
     // Track successful workflow creation
     telemetry.trackWorkflowCreation(workflow, true);
@@ -540,10 +563,8 @@ export async function handleUpdateWorkflow(args: unknown, context?: InstanceCont
         };
       }
 
-      // Normalize all node types before validation
-      const normalizedWorkflow = NodeTypeNormalizer.normalizeWorkflowNodeTypes(fullWorkflow);
-
-      const errors = validateWorkflowStructure(normalizedWorkflow);
+      // Validate workflow structure (n8n API expects FULL form: n8n-nodes-base.*)
+      const errors = validateWorkflowStructure(fullWorkflow);
       if (errors.length > 0) {
         return {
           success: false,
@@ -551,11 +572,6 @@ export async function handleUpdateWorkflow(args: unknown, context?: InstanceCont
           details: { errors }
         };
       }
-
-      // Update updateData with normalized nodes if they were modified
-      if (updateData.nodes) {
-        updateData.nodes = normalizedWorkflow.nodes;
-      }
     }
     
     // Update workflow

src/utils/node-type-normalizer.ts

@@ -1,27 +1,44 @@
 /**
- * Universal Node Type Normalizer
+ * Universal Node Type Normalizer - FOR DATABASE OPERATIONS ONLY
  *
- * Converts ANY node type variation to the canonical SHORT form used by the database.
- * This fixes the critical issue where AI agents or external sources may produce
- * full-form node types (e.g., "n8n-nodes-base.webhook") which need to be normalized
- * to match the database storage format (e.g., "nodes-base.webhook").
+ * ⚠️ WARNING: Do NOT use before n8n API calls!
+ *
+ * This class converts node types to SHORT form (database format).
+ * The n8n API requires FULL form (n8n-nodes-base.*).
+ *
+ * **Use this ONLY when:**
+ * - Querying the node database
+ * - Searching for node information
+ * - Looking up node metadata
+ *
+ * **Do NOT use before:**
+ * - Creating workflows (n8n_create_workflow)
+ * - Updating workflows (n8n_update_workflow)
+ * - Any n8n API calls
  *
  * **IMPORTANT:** The n8n-mcp database stores nodes in SHORT form:
  * - n8n-nodes-base → nodes-base
  * - @n8n/n8n-nodes-langchain → nodes-langchain
  *
- * Handles:
- * - Full form → Short form (n8n-nodes-base.X → nodes-base.X)
- * - Already short form → Unchanged
- * - LangChain nodes → Proper short prefix
+ * But the n8n API requires FULL form:
+ * - nodes-base → n8n-nodes-base
+ * - nodes-langchain → @n8n/n8n-nodes-langchain
  *
- * @example
- * NodeTypeNormalizer.normalizeToFullForm('n8n-nodes-base.webhook')
+ * @example Database Lookup (CORRECT usage)
+ * const dbType = NodeTypeNormalizer.normalizeToFullForm('n8n-nodes-base.webhook')
  * // → 'nodes-base.webhook'
+ * const node = await repository.getNode(dbType)
  *
- * @example
- * NodeTypeNormalizer.normalizeToFullForm('nodes-base.webhook')
- * // → 'nodes-base.webhook' (unchanged)
+ * @example API Call (INCORRECT - Do NOT do this!)
+ * const workflow = { nodes: [{ type: 'n8n-nodes-base.webhook' }] }
+ * const normalized = NodeTypeNormalizer.normalizeWorkflowNodeTypes(workflow)
+ * // ❌ WRONG! normalized has SHORT form, API needs FULL form
+ * await client.createWorkflow(normalized) // FAILS!
+ *
+ * @example API Call (CORRECT)
+ * const workflow = { nodes: [{ type: 'n8n-nodes-base.webhook' }] }
+ * // ✅ Send as-is to API (FULL form required)
+ * await client.createWorkflow(workflow) // WORKS!
  */
 
 export interface NodeTypeNormalizationResult {