feat(lotus): tell the host when the call drops, and let it press Reconnect (cinny #318)

After a homeserver stall the frame shows "Connection lost · Reconnect"
while the host kept showing the call as joined, with controls that did
nothing. While the error page is up, report io.lotus.call_error
{ code, recoverable } (and { code: null } when it clears), and accept
io.lotus.reconnect to run the page's own Reconnect / Try again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/lotus/lotusActions.test.ts

@@ -34,6 +34,7 @@ describe("LotusWidgetActions", () => {
       LotusWidgetActions.SetHotkeys,
       LotusWidgetActions.SetFrameScreenshare,
       LotusWidgetActions.PromptScreenshare,
+      LotusWidgetActions.Reconnect,
     ];
 
     expect(new Set(LOTUS_TO_WIDGET_ACTIONS)).toEqual(new Set(expectedToWidget));
@@ -56,5 +57,6 @@ describe("LotusWidgetActions", () => {
     );
     expect(LOTUS_TO_WIDGET_ACTIONS).not.toContain(LotusWidgetActions.MicLevel);
     expect(LOTUS_TO_WIDGET_ACTIONS).not.toContain(LotusWidgetActions.Hotkey);
+    expect(LOTUS_TO_WIDGET_ACTIONS).not.toContain(LotusWidgetActions.CallError);
   });
 });

src/lotus/lotusActions.ts

@@ -116,6 +116,14 @@ export enum LotusWidgetActions {
    * only when it changes (≤ 10 Hz); 0 while muted or with no mic.
    */
   MicLevel = "io.lotus.mic_level",
+  /**
+   * fromWidget: the call's error page is up (`{ code, recoverable }`) or
+   * cleared (`{ code: null }`) (cinny #318), so the host stops showing the call
+   * as joined after "Connection lost".
+   */
+  CallError = "io.lotus.call_error",
+  /** toWidget: press the error page's Reconnect / Try again (cinny #318). */
+  Reconnect = "io.lotus.reconnect",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
@@ -133,4 +141,5 @@ export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
   LotusWidgetActions.SetHotkeys,
   LotusWidgetActions.SetFrameScreenshare,
   LotusWidgetActions.PromptScreenshare,
+  LotusWidgetActions.Reconnect,
 ];

src/room/GroupCallErrorBoundary.tsx

@@ -13,6 +13,7 @@ import {
   type ReactNode,
   type SVGAttributes,
   useCallback,
+  useEffect,
 } from "react";
 import { Trans, useTranslation } from "react-i18next";
 import {
@@ -24,6 +25,7 @@ import {
 import { Button } from "@vector-im/compound-web";
 import { logger } from "matrix-js-sdk/lib/logger";
 import { MatrixError } from "matrix-js-sdk";
+import { type IWidgetApiRequest } from "matrix-widget-api";
 
 import {
   ConnectionLostError,
@@ -38,6 +40,7 @@ import { FullScreenView } from "../FullScreenView.tsx";
 import { ErrorView } from "../ErrorView.tsx";
 import { type WidgetHelpers } from "../widget.ts";
 import styles from "../ErrorView.module.css";
+import { LotusWidgetActions, lotusSendToHost } from "../lotus/lotusWidget";
 
 export type CallErrorRecoveryAction = "reconnect"; // | "retry" ;
 
@@ -74,6 +77,29 @@ const ErrorPage: FC<ErrorPageProps> = ({
       icon = ErrorSolidIcon;
   }
 
+  // [cinny #318] Tell the host the call dropped (it kept showing the call as
+  // joined), and let its call bar press Reconnect for us.
+  const recoverable =
+    error instanceof ConnectionLostError ||
+    error instanceof LivekitConnectionError ||
+    error instanceof PeerConnectionTimeoutError;
+  useEffect(() => {
+    lotusSendToHost(LotusWidgetActions.CallError, {
+      code: error.code,
+      recoverable,
+    });
+    const w = widget;
+    const onReconnect = (ev: CustomEvent<IWidgetApiRequest>): void => {
+      w?.api.transport.reply(ev.detail, {});
+      if (recoverable) void recoveryActionHandler("reconnect");
+    };
+    w?.lazyActions?.on(LotusWidgetActions.Reconnect, onReconnect);
+    return (): void => {
+      w?.lazyActions?.off(LotusWidgetActions.Reconnect, onReconnect);
+      lotusSendToHost(LotusWidgetActions.CallError, { code: null });
+    };
+  }, [error.code, recoverable, recoveryActionHandler, widget]);
+
   const actions: { label: string; onClick: () => void }[] = [];
   if (error instanceof ConnectionLostError) {
     actions.push({