chore: document intentional picked:true asymmetry in skills picker

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: njb90

src/commands/configureAiTools.ts

@@ -537,7 +537,7 @@ function registerConfigureAiTools(context: vscode.ExtensionContext): void {
             label: s.name,
             description: s.description,
             detail: installedDirNames.has(s.dirName) ? "✓ installed" : "Not installed",
-            picked: true,
+            picked: true, // always pre-selected; writeWithOverwriteCheck guards re-installs
           })),
           { canPickMany: true, placeHolder: "Select skills to install" }
         );