Forum README: correct the Synology permission notes

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDRjtmAiNpo5mK5N3d7QwZ

forum/README.md

@@ -108,14 +108,18 @@ the existing folder (it contains no `config.php`), then `php flarum migrate` and
         --no-same-owner --no-same-permissions --exclude=./storage --exclude=./public/assets' \
         < forum/import/forum.tar.gz
 
-`--no-overwrite-dir` matters on the Synology: without it tar resets the folders it touches to
-plain Unix permissions, which drops the ACL entry that lets `http` write, and the forum answers
-500. Repair, as the folder's owner (repeat for `public`, `public/assets`, `vendor`, `packages`):
+Unpacking resets the folders it touches to plain Unix permissions on the Synology (even with
+`--no-overwrite-dir`), which drops the ACL entry that lets `http` write: the forum then answers
+500. Repair, as the folder's owner (the forum folder, `public`, `public/assets`, `vendor`,
+`packages`):
 
     /usr/syno/bin/synoacltool -add <folder> "user:http:allow:rwxpdDaARWc--:fd--"
 
 and add the same entry for your own account and `group:administrators` right after, or the
-folder is closed to you.
+folder is closed to you. Do not use `-enforce-inherit` or `-copy` on a plain-permission file:
+they leave it with an empty ACL (no access at all; `chmod 644`/`755` brings it back). The
+simpler alternative, used for the WordPress folder: plain permissions with the group `http`
+(`chgrp -R http . && chmod -R g+rwX .`).
 
 The bundle includes the spam filter `fof/anti-spam` (StopForumSpam check at registration, tools
 to remove a spammer); enable it with `php flarum extension:enable fof-anti-spam` (it needs