feat: move web endpoint into a first-party plugin

plugins/web-endpoint/frontend/index.mjs

@@ -0,0 +1,39 @@
+/**
+ * Frontend half of the web-endpoint plugin.
+ *
+ * Registers the endpoint viewer tab through the existing registerTabComponent
+ * seam the same way network-topology's frontend does.
+ *
+ * HostEditorWebUiSection stays in src/ui/sidebar/ rather than moving here, and
+ * is not registered through registerHostEditorTab: it is a section inside the
+ * host editor's existing General tab, not a tab of its own, and it takes the
+ * same {form, setField} pair every other host editor field does -- those types
+ * (HostEditorForm, the setField signature) are core types HostEditor.tsx owns,
+ * the same reason docker leaves HostDockerTab in core rather than copying it
+ * into plugins/docker.
+ *
+ * register() is called when the plugin is enabled, unregister() when it is
+ * disabled. As of this change neither is actually invoked anywhere yet -- see
+ * src/ui/shell/pluginLoader.ts and
+ * src/ui/tests/sidebar/plugin-extension-seam.test.tsx, which says outright
+ * "there is no plugin loader yet" for the frontend half. Until one exists the
+ * tab is rendered directly by tabUtils.tsx and merely gated on the plugin's
+ * enabled state through BUILT_IN_TABS_BY_PLUGIN. This file follows the same
+ * shape every other plugin's frontend entry does so it is ready the moment a
+ * real loader lands.
+ */
+
+export const id = "web-endpoint";
+export const tabId = "web-endpoint";
+
+export async function register({ registerTabComponent }) {
+  registerTabComponent?.(tabId, () =>
+    import("./WebEndpointTab.tsx").then((m) => ({
+      default: m.WebEndpointTab,
+    })),
+  );
+}
+
+export async function unregister({ unregisterTabComponent }) {
+  unregisterTabComponent?.(tabId);
+}