fix: player list styling and positioning tweaks

- Empty slots use subtle gray dashed line instead of solid characters
- Left/Right positions anchor to screen edges, never obscuring room code
- Player list enabled by default
- Fix VALID_TRANSITIONS.get() crash (plain object, not Map)

Made-with: Cursor

js/state-manager.js

@@ -331,7 +331,7 @@ export class OverlayManager {
    */
   #transitionTo(next) {
     const current = this.#state;
-    if (!VALID_TRANSITIONS.get(current)?.has(next)) {
+    if (!VALID_TRANSITIONS[current]?.has(next)) {
       return;
     }