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/vscode/webview/api/editor.ts

@@ -6,7 +6,13 @@ export const createVSCodeEditorAPI = (): EditorAPI => ({
   openFile: async (path: string, line?: number, column?: number) => {
     await sendBridgeMessage('editor:openFile', { path, line, column });
   },
-  openDiff: async (original: string, modified: string, label?: string) => {
-    await sendBridgeMessage('editor:openDiff', { original, modified, label });
+  openDiff: async (original: string, modified: string, label?: string, options?: { line?: number; patch?: string }) => {
+    await sendBridgeMessage('editor:openDiff', {
+      original,
+      modified,
+      label,
+      line: options?.line,
+      patch: options?.patch,
+    });
   },
 });