fix(presence): relay presence-leave messages and clean up listener on disconnect

- Server now relays presence-leave alongside presence messages for immediate peer removal
- Overlay properly unsubscribes leave listener on disconnectedCallback

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/index.ts

@@ -3451,10 +3451,10 @@ const server = Bun.serve<WSData>({
 					}
 				} else if (msg.type === "ping") {
 					ws.send(JSON.stringify({ type: "pong", timestamp: msg.timestamp }));
-				} else if (msg.type === "presence") {
+				} else if (msg.type === "presence" || msg.type === "presence-leave") {
 					const clients = communityClients.get(communitySlug);
 					if (clients) {
-						const presenceMsg = JSON.stringify({ type: "presence", peerId, ...msg });
+						const presenceMsg = JSON.stringify({ ...msg, peerId });
 						for (const [clientPeerId, client] of clients) {
 							if (clientPeerId !== peerId && client.readyState === WebSocket.OPEN) {
 								client.send(presenceMsg);

shared/components/rstack-collab-overlay.ts

@@ -106,6 +106,7 @@ export class RStackCollabOverlay extends HTMLElement {
 			window.removeEventListener('rspace-doc-subscribe', this.#onDocSubscribe);
 			this.#unsubAwareness?.();
 			this.#unsubPresence?.();
+			this.#unsubLeave?.();
 			this.#stopMouseTracking();
 			this.#stopFocusTracking();
 		}