fix: use 'updates' property consistently in updateNode operations

- Changed UpdateNodeOperation interface to use 'updates' instead of 'changes'
- Updated UpdateConnectionOperation for consistency
- Fixed implementation in workflow-diff-engine.ts
- Updated Zod schema validation
- Fixed documentation and examples
- Updated tests to match new property name

This resolves GitHub issues #159 and #168 where partial workflow updates
were failing, forcing AI agents to fall back to expensive full updates.

🤖 Generated with Claude Code

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

tests/unit/services/workflow-diff-engine.test.ts

@@ -281,7 +281,7 @@ describe('WorkflowDiffEngine', () => {
       const operation: UpdateNodeOperation = {
         type: 'updateNode',
         nodeId: 'http-1',
-        changes: {
+        updates: {
           'parameters.method': 'POST',
           'parameters.url': 'https://new-api.example.com'
         }
@@ -304,7 +304,7 @@ describe('WorkflowDiffEngine', () => {
       const operation: UpdateNodeOperation = {
         type: 'updateNode',
         nodeName: 'Slack',
-        changes: {
+        updates: {
           'parameters.resource': 'channel',
           'parameters.operation': 'create',
           'credentials.slackApi.name': 'New Slack Account'
@@ -329,7 +329,7 @@ describe('WorkflowDiffEngine', () => {
       const operation: UpdateNodeOperation = {
         type: 'updateNode',
         nodeId: 'non-existent',
-        changes: {
+        updates: {
           'parameters.test': 'value'
         }
       };
@@ -617,7 +617,7 @@ describe('WorkflowDiffEngine', () => {
         type: 'updateConnection',
         source: 'IF',
         target: 'slack-1',
-        changes: {
+        updates: {
           sourceOutput: 'false',
           sourceIndex: 0,
           targetIndex: 0
@@ -1039,7 +1039,7 @@ describe('WorkflowDiffEngine', () => {
       const operation: UpdateNodeOperation = {
         type: 'updateNode',
         nodeId: 'Webhook', // Using name as ID
-        changes: {
+        updates: {
           'parameters.path': 'new-webhook-path'
         }
       };