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/desktop/src/local-server.ts

@@ -0,0 +1,90 @@
+import type { AddressInfo } from "node:net";
+import { once } from "node:events";
+import type { Server } from "node:http";
+type TaskStoreLike = {
+  init(): Promise<void>;
+  watch(): Promise<void>;
+  close(): void;
+};
+
+export interface DesktopLocalRuntime {
+  store: TaskStoreLike;
+  server: Server;
+  port: number;
+}
+
+export interface DesktopLocalServerState {
+  status: "idle" | "starting" | "ready" | "error";
+  port?: number;
+  error?: string | null;
+}
+
+export class DesktopLocalServerManager {
+  private runtime: DesktopLocalRuntime | null = null;
+  private state: DesktopLocalServerState = { status: "idle", error: null };
+
+  constructor(private readonly rootDir: string) {}
+
+  getState(): DesktopLocalServerState {
+    return this.state;
+  }
+
+  getPort(): number | undefined {
+    return this.runtime?.port;
+  }
+
+  async start(): Promise<DesktopLocalRuntime> {
+    if (this.runtime) {
+      this.state = { status: "ready", port: this.runtime.port, error: null };
+      return this.runtime;
+    }
+
+    this.state = { status: "starting", error: null };
+
+    try {
+      const { TaskStore } = await import("@fusion/core");
+      const { createServer } = await import("@fusion/dashboard");
+      const store = new TaskStore(this.rootDir) as TaskStoreLike;
+      await store.init();
+      await store.watch();
+      const app = createServer(store);
+      const server = app.listen(0);
+
+      await Promise.race([
+        once(server, "listening"),
+        once(server, "error").then(([error]) => {
+          throw error;
+        }),
+      ]);
+
+      const address = server.address() as AddressInfo | null;
+      if (!address?.port) {
+        throw new Error("Failed to resolve local server port");
+      }
+
+      this.runtime = { store, server, port: address.port };
+      this.state = { status: "ready", port: address.port, error: null };
+      return this.runtime;
+    } catch (error) {
+      this.state = {
+        status: "error",
+        error: error instanceof Error ? error.message : String(error),
+      };
+      throw error;
+    }
+  }
+
+  async stop(): Promise<void> {
+    if (!this.runtime) {
+      this.state = { status: "idle", error: null };
+      return;
+    }
+
+    const runtime = this.runtime;
+    this.runtime = null;
+
+    await new Promise<void>((resolve) => runtime.server.close(() => resolve()));
+    runtime.store.close();
+    this.state = { status: "idle", error: null };
+  }
+}