fix: convert ES modules to classic scripts for file:// compatibility

Browsers block ES module imports over the file:// protocol due to CORS.
Users opening the overlay by double-clicking the HTML file saw all JS
fail to load. Replace import/export with a window.OBS global namespace
and classic <script> tags so the overlay works without a local server.

Made-with: Cursor

js/state-manager.js

@@ -2,7 +2,7 @@
  * Central overlay state machine: coordinates room/game lifecycle and registered UI components.
  */
 
-export const OVERRIDE_MODES = Object.freeze({
+const OVERRIDE_MODES = Object.freeze({
   AUTO: 'auto',
   FORCE_SHOW: 'force_show',
   FORCE_HIDE: 'force_hide',
@@ -34,7 +34,7 @@ function shallowClone(obj) {
  * @property {() => object} getStatus
  */
 
-export class OverlayManager {
+class OverlayManager {
   /** @type {OverlayState} */
   #state = 'idle';
 
@@ -414,3 +414,7 @@ export class OverlayManager {
     }
   }
 }
+
+window.OBS = window.OBS || {};
+window.OBS.OVERRIDE_MODES = OVERRIDE_MODES;
+window.OBS.OverlayManager = OverlayManager;