feat: Add workflow activation/deactivation via diff operations

Implements workflow activation and deactivation as diff operations in
n8n_update_partial_workflow tool, following the pattern of other
configuration operations.

Changes:
- Add activateWorkflow/deactivateWorkflow API methods
- Add operation types to diff engine
- Update tool documentation
- Remove activation limitation

Resolves #399
Credits: ArtemisAI, cmj-hub for investigation and initial implementation
Conceived by Romuald Członkowski - www.aiadvisors.pl/en

src/mcp/handlers-n8n-manager.ts

@@ -1561,7 +1561,6 @@ export async function handleListAvailableTools(context?: InstanceContext): Promi
         maxRetries: config.maxRetries
       } : null,
       limitations: [
-        'Cannot activate/deactivate workflows via API',
         'Cannot execute workflows directly (must use webhooks)',
         'Cannot stop running executions',
         'Tags and credentials have limited API support'

src/mcp/handlers-workflow-diff.ts

@@ -245,15 +245,52 @@ export async function handleUpdatePartialWorkflow(
     // Update workflow via API
     try {
       const updatedWorkflow = await client.updateWorkflow(input.id, diffResult.workflow!);
-      
+
+      // Handle activation/deactivation if requested
+      let finalWorkflow = updatedWorkflow;
+      let activationMessage = '';
+
+      if (diffResult.shouldActivate) {
+        try {
+          finalWorkflow = await client.activateWorkflow(input.id);
+          activationMessage = ' Workflow activated.';
+        } catch (activationError) {
+          logger.error('Failed to activate workflow after update', activationError);
+          return {
+            success: false,
+            error: 'Workflow updated successfully but activation failed',
+            details: {
+              workflowUpdated: true,
+              activationError: activationError instanceof Error ? activationError.message : 'Unknown error'
+            }
+          };
+        }
+      } else if (diffResult.shouldDeactivate) {
+        try {
+          finalWorkflow = await client.deactivateWorkflow(input.id);
+          activationMessage = ' Workflow deactivated.';
+        } catch (deactivationError) {
+          logger.error('Failed to deactivate workflow after update', deactivationError);
+          return {
+            success: false,
+            error: 'Workflow updated successfully but deactivation failed',
+            details: {
+              workflowUpdated: true,
+              deactivationError: deactivationError instanceof Error ? deactivationError.message : 'Unknown error'
+            }
+          };
+        }
+      }
+
       return {
         success: true,
-        data: updatedWorkflow,
-        message: `Workflow "${updatedWorkflow.name}" updated successfully. Applied ${diffResult.operationsApplied} operations.`,
+        data: finalWorkflow,
+        message: `Workflow "${finalWorkflow.name}" updated successfully. Applied ${diffResult.operationsApplied} operations.${activationMessage}`,
         details: {
           operationsApplied: diffResult.operationsApplied,
-          workflowId: updatedWorkflow.id,
-          workflowName: updatedWorkflow.name,
+          workflowId: finalWorkflow.id,
+          workflowName: finalWorkflow.name,
+          active: finalWorkflow.active,
           applied: diffResult.applied,
           failed: diffResult.failed,
           errors: diffResult.errors,

src/mcp/tool-docs/workflow_management/n8n-update-partial-workflow.ts

@@ -4,7 +4,7 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
   name: 'n8n_update_partial_workflow',
   category: 'workflow_management',
   essentials: {
-    description: 'Update workflow incrementally with diff operations. Types: addNode, removeNode, updateNode, moveNode, enable/disableNode, addConnection, removeConnection, rewireConnection, cleanStaleConnections, replaceConnections, updateSettings, updateName, add/removeTag. Supports smart parameters (branch, case) for multi-output nodes. Full support for AI connections (ai_languageModel, ai_tool, ai_memory, ai_embedding, ai_vectorStore, ai_document, ai_textSplitter, ai_outputParser).',
+    description: 'Update workflow incrementally with diff operations. Types: addNode, removeNode, updateNode, moveNode, enable/disableNode, addConnection, removeConnection, rewireConnection, cleanStaleConnections, replaceConnections, updateSettings, updateName, add/removeTag, activateWorkflow, deactivateWorkflow. Supports smart parameters (branch, case) for multi-output nodes. Full support for AI connections (ai_languageModel, ai_tool, ai_memory, ai_embedding, ai_vectorStore, ai_document, ai_textSplitter, ai_outputParser).',
     keyParameters: ['id', 'operations', 'continueOnError'],
     example: 'n8n_update_partial_workflow({id: "wf_123", operations: [{type: "rewireConnection", source: "IF", from: "Old", to: "New", branch: "true"}]})',
     performance: 'Fast (50-200ms)',
@@ -19,11 +19,12 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
       'For AI connections, specify sourceOutput type (ai_languageModel, ai_tool, etc.)',
       'Batch AI component connections for atomic updates',
       'Auto-sanitization: ALL nodes auto-fixed during updates (operator structures, missing metadata)',
-      'Node renames automatically update all connection references - no manual connection operations needed'
+      'Node renames automatically update all connection references - no manual connection operations needed',
+      'Activate/deactivate workflows: Use activateWorkflow/deactivateWorkflow operations (requires activatable triggers like webhook/schedule)'
     ]
   },
   full: {
-    description: `Updates workflows using surgical diff operations instead of full replacement. Supports 15 operation types for precise modifications. Operations are validated and applied atomically by default - all succeed or none are applied.
+    description: `Updates workflows using surgical diff operations instead of full replacement. Supports 17 operation types for precise modifications. Operations are validated and applied atomically by default - all succeed or none are applied.
 
 ## Available Operations:
 
@@ -48,6 +49,10 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
 - **addTag**: Add a workflow tag
 - **removeTag**: Remove a workflow tag
 
+### Workflow Activation Operations (2 types):
+- **activateWorkflow**: Activate the workflow to enable automatic execution via triggers
+- **deactivateWorkflow**: Deactivate the workflow to prevent automatic execution
+
 ## Smart Parameters for Multi-Output Nodes
 
 For **IF nodes**, use semantic 'branch' parameter instead of technical sourceIndex: