fix(plugins): isole les contributions plugin en erreur et durcit menus.ts

Le chargement de l'archive hello-plugin (build/hello-plugin-0.1.0.zip)
vidait la fenêtre principale : une contribution plugin fautive
remontait jusqu'au rendu global au lieu de rester locale à la cellule.
Ajoute un boundary local dans PluginLayoutCellView/PluginLayoutSelectorSection
et durcit menus.ts/loader.ts/registry.ts contre les entrées de menu ou
contributions malformées.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/features/plugins/menus.test.ts

@@ -59,6 +59,23 @@ describe("resolveTopLevelMenus", () => {
     const resolved = resolveTopLevelMenus(registry);
     expect(resolved.map((m) => m.label)).toEqual(["Z Menu", "A Menu", "B Menu"]);
   });
+
+  it("drops malformed top-level menus instead of throwing during resolution", () => {
+    const registry = new PluginRuntimeRegistry();
+    registry.add(
+      stubPlugin("dev.bad", "Bad", {
+        ...empty(),
+        menus: [
+          { id: "bad.menu", label: "Good", topLevel: true },
+          { id: "bad.empty", label: "", topLevel: true },
+          { id: undefined, label: "No id", topLevel: true },
+          { id: "bad.no-label", label: undefined, topLevel: true },
+        ] as unknown as PluginContributionDto["menus"],
+      }),
+    );
+
+    expect(resolveTopLevelMenus(registry).map((m) => m.label)).toEqual(["Good"]);
+  });
 });
 
 describe("resolveMenuItems", () => {
@@ -137,6 +154,36 @@ describe("resolveMenuItems", () => {
     expect(items.map((i) => i.label)).toEqual(["A item", "Z item"]);
   });
 
+  it("resolves hello-plugin's bare plugin menu target and skips malformed items", () => {
+    const registry = new PluginRuntimeRegistry();
+    registry.add(
+      stubPlugin("com.example.hello-plugin", "Hello Plugin", {
+        ...empty(),
+        menus: [{ id: "hello-plugin.menu", label: "Hello", topLevel: true }],
+        menuItems: [
+          {
+            id: "hello-plugin.sayHello.item",
+            targetMenuId: "hello-plugin.menu",
+            label: "Say Hello",
+            command: "hello-plugin.sayHello",
+          },
+          {
+            id: "hello-plugin.broken.item",
+            targetMenuId: "hello-plugin.menu",
+            label: undefined,
+            command: "hello-plugin.broken",
+          },
+        ] as unknown as PluginContributionDto["menuItems"],
+      }),
+    );
+
+    const menus = resolveTopLevelMenus(registry);
+    expect(menus.map((m) => m.id)).toEqual(["plugin:hello-plugin.menu"]);
+    const items = resolveMenuItems(registry, "plugin:hello-plugin.menu", NO_CONTEXT);
+    expect(items.map((i) => i.label)).toEqual(["Say Hello"]);
+    expect(items[0].targetMenuId).toBe("plugin:hello-plugin.menu");
+  });
+
   it("dispatches a command via the registry's runCommand", async () => {
     const registry = new PluginRuntimeRegistry();
     let ran = false;