FRE-600: Fix code review blockers

- Consolidated duplicate UndoManagers to single instance
- Fixed connection promise to only resolve on 'connected' status
- Fixed WebSocketProvider import (WebsocketProvider)
- Added proper doc.destroy() cleanup
- Renamed isPresenceInitialized property to avoid conflict

Co-Authored-By: Paperclip <noreply@paperclip.ing>

node_modules/seroval-plugins/web/headers.ts

@@ -0,0 +1,49 @@
+import type { SerovalNode } from 'seroval';
+import { createPlugin } from 'seroval';
+
+function convertHeaders(instance: Headers): HeadersInit {
+  const items: HeadersInit = [];
+  // biome-ignore lint/complexity/noForEach: <explanation>
+  instance.forEach((value, key) => {
+    items.push([key, value]);
+  });
+  return items;
+}
+
+const HeadersPlugin = /* @__PURE__ */ createPlugin<
+  Headers,
+  { value: SerovalNode }
+>({
+  tag: 'seroval-plugins/web/Headers',
+  test(value) {
+    if (typeof Headers === 'undefined') {
+      return false;
+    }
+    return value instanceof Headers;
+  },
+  parse: {
+    sync(value, ctx) {
+      return {
+        value: ctx.parse(convertHeaders(value)),
+      };
+    },
+    async async(value, ctx) {
+      return {
+        value: await ctx.parse(convertHeaders(value)),
+      };
+    },
+    stream(value, ctx) {
+      return {
+        value: ctx.parse(convertHeaders(value)),
+      };
+    },
+  },
+  serialize(node, ctx) {
+    return 'new Headers(' + ctx.serialize(node.value) + ')';
+  },
+  deserialize(node, ctx) {
+    return new Headers(ctx.deserialize(node.value) as HeadersInit);
+  },
+});
+
+export default HeadersPlugin;