docs(06): create phase plan for n8n API access

Phase 6: n8n API Access
- 1 plan in 1 wave
- Covers API-01 through API-04 requirements
- Human checkpoint for API key creation + automated verification
- Fixed: Use PUT (not PATCH) per current n8n docs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/phases/06-n8n-api-access/06-RESEARCH.md

@@ -103,7 +103,7 @@ const updated = await n8nClient.patch(`/api/v1/workflows/${workflowId}`, {
 **When to use:** Making incremental changes to existing workflows
 **Example:**
 ```javascript
-// Source: Community workflow manager patterns
+// Source: n8n official docs - public API uses PUT (full replace)
 async function updateWorkflowNode(workflowId, nodeName, newParams) {
   // 1. Fetch current workflow
   const { data: workflow } = await n8nClient.get(`/api/v1/workflows/${workflowId}`);
@@ -114,8 +114,9 @@ async function updateWorkflowNode(workflowId, nodeName, newParams) {
     node.parameters = { ...node.parameters, ...newParams };
   }
 
-  // 3. Push updated workflow
-  const { data: updated } = await n8nClient.patch(`/api/v1/workflows/${workflowId}`, {
+  // 3. Push updated workflow (PUT requires full workflow body)
+  const { data: updated } = await n8nClient.put(`/api/v1/workflows/${workflowId}`, {
+    name: workflow.name,
     nodes: workflow.nodes,
     connections: workflow.connections,
     settings: workflow.settings
@@ -275,16 +276,19 @@ curl -X GET 'http://localhost:5678/api/v1/workflows/1' \
   -H 'X-N8N-API-KEY: n8n_api_...'
 ```
 
-### Update Workflow (Partial)
+### Update Workflow (Full Replace)
 ```bash
-# Source: Community workflow manager patterns
-curl -X PATCH 'http://localhost:5678/api/v1/workflows/1' \
+# Source: n8n official docs - public API uses PUT for workflow updates
+# Note: Must include name, nodes, connections, settings (full workflow body)
+curl -X PUT 'http://localhost:5678/api/v1/workflows/1' \
   -H 'accept: application/json' \
   -H 'X-N8N-API-KEY: n8n_api_...' \
   -H 'Content-Type: application/json' \
   -d '{
+    "name": "Workflow Name",
     "nodes": [...updated nodes array...],
-    "connections": {...updated connections...}
+    "connections": {...updated connections...},
+    "settings": {}
   }'
 ```