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>

src/types/workflow-diff.ts

@@ -31,7 +31,7 @@ export interface UpdateNodeOperation extends DiffOperation {
   type: 'updateNode';
   nodeId?: string; // Can use either ID or name
   nodeName?: string;
-  changes: {
+  updates: {
     [path: string]: any; // Dot notation paths like 'parameters.url'
   };
 }
@@ -78,7 +78,7 @@ export interface UpdateConnectionOperation extends DiffOperation {
   type: 'updateConnection';
   source: string;
   target: string;
-  changes: {
+  updates: {
     sourceOutput?: string;
     targetInput?: string;
     sourceIndex?: number;