chore(types): fewer any casts; eslint warning ratchet 36 -> 29 (#210)

- Developer tools (send event, state event editor, room account data) and
  setMarkedUnread go through the typed helpers in utils/room and
  utils/accountData (new setRoomAccountData) instead of casting at the
  call site; sendStateEvent accepts a developer-chosen type string.
- SecretStorage passes the key description as the SDK's
  SecretStorageKeyDescription, CallEmbed replies with an IWidgetApiRequest,
  and fillMissingPowers writes through a Record instead of `as any`.

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

src/app/utils/accountData.ts

@@ -18,6 +18,17 @@ export function getAccountData<T>(
   return event?.getContent() as T | undefined;
 }
 
+/** Room account data under a custom or developer-chosen type (same cast). */
+export function setRoomAccountData<T>(
+  mx: MatrixClient,
+  roomId: string,
+  eventType: string,
+  content: T,
+): Promise<unknown> {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return (mx as any).setRoomAccountData(roomId, eventType, content);
+}
+
 export function setAccountData<T>(
   mx: MatrixClient,
   eventType: AccountDataEvent | string,