[lib] Hide initialThreadState.memberIDs from GENESIS

Summary:
We hide the members list of GENESIS. For similar reasons, we should hide the list of initial members.

This addresses [ENG-9430](https://linear.app/comm/issue/ENG-9430/hide-initialthreadstatememberids-list-on-genesis); more context there.

Test Plan: I added an `|| true`, and then logged out and back in on `web` and confirmed that all thread creation robotext were missing "and added A and B" at the end

Reviewers: varun, will

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13528

lib/shared/messages/create-thread-message-spec.js

@@ -9,6 +9,7 @@ import {
   type RobotextParams,
 } from './message-spec.js';
 import { assertSingleMessageInfo } from './utils.js';
+import genesis from '../../facts/genesis.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type {
   ClientDBMessageInfo,
@@ -56,13 +57,21 @@ export const createThreadMessageSpec: CreateThreadMessageSpec = Object.freeze({
   },
 
   rawMessageInfoFromServerDBRow(row: Object): RawCreateThreadMessageInfo {
+    const threadID = row.threadID.toString();
+    let initialThreadState = JSON.parse(row.content);
+    if (threadID === genesis().id) {
+      initialThreadState = {
+        ...initialThreadState,
+        memberIDs: [],
+      };
+    }
     return {
       type: messageTypes.CREATE_THREAD,
       id: row.id.toString(),
-      threadID: row.threadID.toString(),
+      threadID,
       time: row.time,
       creatorID: row.creatorID.toString(),
-      initialThreadState: JSON.parse(row.content),
+      initialThreadState,
     };
   },