refactor: unify bun compiled detection with windows support

- Add shared isBunCompiled() function for consistent runtime detection
- Support Windows virtual filesystem paths (/~BUN/) alongside Linux/macOS (/$bunfs/)
- Use Bun.main for reliable detection instead of process.argv[1]
- Remove redundant $bunfs checks from cli/src/index.ts
- Update cli/src/utils/bunRuntime.ts to use shared detection function
- Create server/src/utils/bunCompiled.ts for server-side compilation check

server/src/utils/bunCompiled.ts

@@ -0,0 +1,4 @@
+/** Bun embeds compiled code in a virtual filesystem: /$bunfs/ (Linux/macOS) or /~BUN/ (Windows) */
+export function isBunCompiled(): boolean {
+    return Bun.main.includes('$bunfs') || Bun.main.includes('/~BUN/');
+}

server/src/web/server.ts

@@ -20,6 +20,7 @@ import type { Server as BunServer } from 'bun'
 import type { Server as SocketEngine } from '@socket.io/bun-engine'
 import type { WebSocketData } from '@socket.io/bun-engine'
 import { loadEmbeddedAssetMap, type EmbeddedWebAsset } from './embeddedAssets'
+import { isBunCompiled } from '../utils/bunCompiled'
 
 function findWebappDistDir(): { distDir: string; indexHtmlPath: string } {
     const candidates = [
@@ -163,7 +164,7 @@ export async function startWebServer(options: {
     jwtSecret: Uint8Array
     socketEngine: SocketEngine
 }): Promise<BunServer<WebSocketData>> {
-    const isCompiled = Bun.main?.startsWith('/$bunfs') ?? false
+    const isCompiled = isBunCompiled()
     const embeddedAssetMap = isCompiled ? await loadEmbeddedAssetMap() : null
     const app = createWebApp({
         getSyncEngine: options.getSyncEngine,