refactor: Modularize JavaScript Code into Separate Files

public/js/session.js

@@ -0,0 +1,23 @@
+import { $nameDisplay, $nameLobby } from './dom.js';
+import { state } from './state.js';
+import { sendMsg } from './ws.js';
+
+// If we have a stored player name, set it in the input and send to server
+export function reusePlayerName() {
+  const stored = localStorage.getItem('playerName');
+  if (!stored) return;
+  if ($nameLobby && $nameLobby.value !== stored) {
+    $nameLobby.value = stored;
+  }
+  if ($nameDisplay) {
+    $nameDisplay.textContent = stored;
+  }
+  sendMsg({ type: 'set_name', name: stored });
+}
+
+export function reconnectLastRoom() {
+  const last = state.room?.id || localStorage.getItem('lastRoomId');
+  if (last && !localStorage.getItem('sessionId')) {
+    sendMsg({ type: 'join_room', code: last });
+  }
+}