feat(FN-3398): update desktop README with multi-project setup and troublesh

The merge lands Step 7 of FN-3398, adding documentation and delivery artifacts across the mobile and desktop packages with updated READMEs, mobile-specific docs, and architecture references.

Fusion-Task-Id: FN-3398

packages/mobile/src/__tests__/native-shell.test.ts

@@ -0,0 +1,62 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const state = {
+  activeProfileId: null as string | null,
+  profiles: [] as Array<{ id: string; name: string; serverUrl: string; authToken?: string | null; createdAt: string; updatedAt: string; lastUsedAt?: string | null }>,
+};
+
+vi.mock("../plugins/connection-profiles.js", () => ({
+  loadShellProfiles: vi.fn(async () => state),
+  listShellProfiles: vi.fn(async () => state.profiles),
+  saveShellProfile: vi.fn(async (profile: { name: string; serverUrl: string }) => {
+    const saved = {
+      id: "p1",
+      name: profile.name,
+      serverUrl: profile.serverUrl,
+      authToken: null,
+      createdAt: "2026-01-01T00:00:00.000Z",
+      updatedAt: "2026-01-01T00:00:00.000Z",
+      lastUsedAt: null,
+    };
+    state.profiles = [saved];
+    return saved;
+  }),
+  deleteShellProfile: vi.fn(async () => {
+    state.profiles = [];
+    state.activeProfileId = null;
+  }),
+  setActiveShellProfile: vi.fn(async (profileId: string | null) => {
+    state.activeProfileId = profileId;
+    return state;
+  }),
+}));
+
+describe("MobileNativeShellBridge", () => {
+  const scanner = { scanConnection: vi.fn(async () => ({ serverUrl: "https://fusion.example.com", authToken: null })) };
+
+  beforeEach(() => {
+    state.activeProfileId = null;
+    state.profiles = [];
+    scanner.scanConnection.mockClear();
+    vi.resetModules();
+  });
+
+  it("emits state updates to subscribers", async () => {
+    const { MobileNativeShellBridge } = await import("../plugins/native-shell.js");
+    const bridge = new MobileNativeShellBridge(scanner as never);
+    const listener = vi.fn();
+
+    const unsubscribe = bridge.subscribe(listener);
+    await bridge.saveProfile({ name: "Prod", serverUrl: "https://fusion.example.com" });
+
+    expect(listener).toHaveBeenCalled();
+    unsubscribe();
+  });
+
+  it("rejects desktop mode switch", async () => {
+    const { MobileNativeShellBridge } = await import("../plugins/native-shell.js");
+    const bridge = new MobileNativeShellBridge(scanner as never);
+
+    await expect(bridge.setDesktopMode("local")).rejects.toThrow("Desktop mode is not supported");
+  });
+});