feat: open edit tool changes in VS Code diff view with line focus

Tool-card clicks for edit-like actions now open a VS Code diff instead of only the file
Diff view focuses the first changed line for faster review
Uses a virtual readonly original buffer to avoid opening unsaved draft tabs

packages/ui/src/lib/api/types.ts

@@ -598,7 +598,12 @@ export interface ToolsAPI {
 
 export interface EditorAPI {
   openFile(path: string, line?: number, column?: number): Promise<void>;
-  openDiff(original: string, modified: string, label?: string): Promise<void>;
+  openDiff(
+    original: string,
+    modified: string,
+    label?: string,
+    options?: { line?: number; patch?: string },
+  ): Promise<void>;
 }
 
 export interface VSCodeAPI {