fix: prevent file drags from replacing the app view (#71)

* fix: prevent dropped files from replacing the app view

* test: use drag events in app navigation test

ui/goose2/src/app/App.test.tsx

@@ -0,0 +1,39 @@
+import { render } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { App } from "./App";
+
+vi.mock("@/app/AppShell", () => ({
+  AppShell: () => <div data-testid="app-shell" />,
+}));
+
+describe("App", () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it("prevents default window navigation when files are dragged into the app", () => {
+    vi.stubGlobal("__TAURI_INTERNALS__", undefined);
+    vi.stubGlobal(
+      "DragEvent",
+      window.DragEvent ?? class DragEvent extends Event {},
+    );
+
+    render(<App />);
+
+    const dragOverEvent = new DragEvent("dragover", {
+      bubbles: true,
+      cancelable: true,
+    });
+    const dropEvent = new DragEvent("drop", {
+      bubbles: true,
+      cancelable: true,
+    });
+
+    window.dispatchEvent(dragOverEvent);
+    window.dispatchEvent(dropEvent);
+
+    expect(dragOverEvent.defaultPrevented).toBe(true);
+    expect(dropEvent.defaultPrevented).toBe(true);
+  });
+});

ui/goose2/src/app/App.tsx

@@ -4,6 +4,13 @@ import { AppShell } from "@/app/AppShell";
 
 export function App() {
   useEffect(() => {
+    const preventWindowFileNavigation = (event: DragEvent) => {
+      event.preventDefault();
+    };
+
+    window.addEventListener("dragover", preventWindowFileNavigation);
+    window.addEventListener("drop", preventWindowFileNavigation);
+
     // Dynamic import to avoid crash in non-Tauri environments (e.g., Playwright E2E)
     if (window.__TAURI_INTERNALS__) {
       import("@tauri-apps/api/window").then(({ getCurrentWindow }) => {
@@ -12,6 +19,11 @@ export function App() {
           .catch(() => {});
       });
     }
+
+    return () => {
+      window.removeEventListener("dragover", preventWindowFileNavigation);
+      window.removeEventListener("drop", preventWindowFileNavigation);
+    };
   }, []);
 
   return <AppShell />;