feat: keep dev server alive during HMR updates

packages/dev-server/src/hmr.ts

@@ -7,9 +7,9 @@
  *   { type: "css" }     -> the browser hot-swaps the stylesheet (no reload)
  *   { type: "reload" }  -> the browser asks for fresh HTML over the HMR socket
  *
- * Server-logic changes (pages/api/middleware/realtime) are NOT broadcast here:
- * they require a fresh process, so the child exits and the supervisor respawns
- * it. The browser then reconnects and performs a soft DOM morph automatically.
+ * Page/component/API/middleware/realtime changes invalidate their modules and
+ * broadcast `reload` without closing the server or WebSocket. The browser asks
+ * the same process for fresh HTML and performs a soft DOM morph.
  */
 
 export type HmrMessage = { type: "css"; version: number } | { type: "reload"; version: number };