feat(FN-3399): route desktop remote mode into shell onboarding flow

Removes the standalone `DesktopShellBootstrap` component from the desktop package, routing desktop remote mode into the shell onboarding flow instead. Updates the corresponding test file to reflect the component removal and adjusts the README.

Fusion-Task-Id: FN-3399

packages/dashboard/app/components/MobileNavBar.tsx

@@ -1,5 +1,5 @@
 import "./MobileNavBar.css";
-import { useCallback, useEffect, useMemo, useState } from "react";
+import { useCallback, useEffect, useMemo, useState, type ReactNode } from "react";
 import {
   Activity,
   Bot,
@@ -85,6 +85,7 @@ export interface MobileNavBarProps {
   };
   onOpenNodes?: () => void;
   pluginDashboardViews?: PluginDashboardViewEntry[];
+  shellConnectionControl?: ReactNode;
 }
 
 function GitHubLogo({ size = 20 }: { size?: number }) {

packages/dashboard/app/context/ShellContext.tsx

@@ -1,7 +1,7 @@
 import { createContext, useContext, useEffect, useMemo, useState, type PropsWithChildren } from "react";
 import type { FusionShellApi, ShellConnectionState } from "../types/native-shell";
 
-interface ShellContextValue {
+export interface ShellContextValue {
   shellApi: FusionShellApi | null;
   state: ShellConnectionState;
   ready: boolean;