F10 SLICE-3: rename preview panel title to 'Review' (#29)

Code-quality polish: the webview panel title read 'Track changes: <name>' but
F10 makes the preview the single review surface. Match the 'Open Review Preview'
command rename.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/trackChangesPreview.ts

@@ -71,7 +71,7 @@ export class TrackChangesPreviewController implements vscode.Disposable {
     const name = path.basename(document.uri.path) || "untitled";
     const panel = vscode.window.createWebviewPanel(
       VIEW_TYPE,
-      `Track changes: ${name}`,
+      `Review: ${name}`,
       { viewColumn: vscode.ViewColumn.Beside, preserveFocus: true },
       {
         enableScripts: true,