Wire up MSC2931 widget navigation

Fixes https://github.com/vector-im/element-web/issues/16006
**Requires https://github.com/matrix-org/matrix-widget-api/pull/27**

src/stores/widgets/ElementWidgetActions.ts

@@ -20,9 +20,16 @@ export enum ElementWidgetActions {
     ClientReady = "im.vector.ready",
     HangupCall = "im.vector.hangup",
     OpenIntegrationManager = "integration_manager_open",
+
+    /**
+     * @deprecated Use MSC2931 instead
+     */
     ViewRoom = "io.element.view_room",
 }
 
+/**
+ * @deprecated Use MSC2931 instead
+ */
 export interface IViewRoomApiRequest extends IWidgetApiRequest {
     data: {
         room_id: string; // eslint-disable-line camelcase

src/stores/widgets/ElementWidgetCapabilities.ts

@@ -15,5 +15,8 @@
  */
 
 export enum ElementWidgetCapabilities {
+    /**
+     * @deprecated Use MSC2931 instead.
+     */
     CanChangeViewedRoom = "io.element.view_room",
 }

src/stores/widgets/StopGapWidgetDriver.ts

@@ -43,6 +43,7 @@ import { EventType } from "matrix-js-sdk/src/@types/event";
 import { CHAT_EFFECTS } from "../../effects";
 import { containsEmoji } from "../../effects/utils";
 import dis from "../../dispatcher/dispatcher";
+import {tryTransformPermalinkToLocalHref} from "../../utils/permalinks/Permalinks";
 
 // TODO: Purge this from the universe
 
@@ -171,4 +172,12 @@ export class StopGapWidgetDriver extends WidgetDriver {
             },
         });
     }
+
+    public async navigate(uri: string): Promise<void> {
+        const localUri = tryTransformPermalinkToLocalHref(uri);
+        if (!localUri || localUri === uri) { // parse failure can lead to an unmodified URL
+            throw new Error("Failed to transform URI");
+        }
+        window.location.hash = localUri; // it'll just be a fragment
+    }
 }