Add Bookmarks example plugin

Adds packages/plugins/examples/plugin-bookmarks-example, a new first-party
"core surface" example that exercises plugin database namespaces, local
folders, scoped API routes, and the page/sidebar/dashboard/settings UI
slots end-to-end. Registers the example as a bundled plugin in
server/src/routes/plugins.ts and excludes its workspace importer in
pnpm-workspace.yaml so PRs don't have to commit lockfile entries for it.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/routes/plugins.ts

@@ -180,6 +180,14 @@ const BUNDLED_PLUGIN_EXAMPLES: AvailablePluginExample[] = [
     localPath: "packages/plugins/examples/plugin-orchestration-smoke-example",
     tag: "example",
   },
+  {
+    packageName: "@paperclipai/plugin-bookmarks-example",
+    pluginKey: "paperclipai.plugin-bookmarks-example",
+    displayName: "Bookmarks (Example)",
+    description: "Company-scoped bookmark library backed by a plugin database namespace and a local markdown folder. Demonstrates scoped API routes, local folders, dashboard widget, and a plugin page.",
+    localPath: "packages/plugins/examples/plugin-bookmarks-example",
+    tag: "example",
+  },
 ];
 
 function listBundledPluginExamples(): AvailablePluginExample[] {