P7: Lemmy's Warn and Resolve{Flag}

- A Warn from a community's moderator about a persona's own post there becomes that persona's moderation_warning
  notification (Mastodon's AccountWarning, with the reason and the post), believed from the community's own server or
  from an account the community's moderators collection lists. Remote communities keep that collection's address
  (attributedTo) as ForeignAvatar.ModeratorsURL; it is read only when a warning needs it.
- A Resolve{Flag} for one of our reports (`/grunts/flag-<report id>`) is kept as the report's remote resolution when it
  comes from the server holding what was reported, or the community it was reported to; our own moderators'
  resolution is never replaced. The moderators' report list shows both.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

docs/ROADMAP.md

@@ -688,7 +688,9 @@ it, raw where it doesn't.
     public and unlisted replies only; Mastodon finds a thread's replies through them, checked live).
 - **Lemmy, PieFed and Mbin:**
   - the moderation set: removals, locks, bans (**done 2026-10-05**, relayed by the community: a lock refuses replies, a
-    ban of a persona refuses its posts there and shows as `blocked_by`), featured, moderators, `Warn`, `Resolve`;
+    ban of a persona refuses its posts there and shows as `blocked_by`), featured; `Warn` and `Resolve` (**done
+    2026-10-07**: a warning becomes the persona's `moderation_warning` notification, believed from the community's
+    server or its moderators collection, kept as `ForeignAvatar.ModeratorsURL`; a resolution is kept on our report);
   - votes in and out; link posts; flairs; `Feed` actors; community polls; post `Move`;
   - the outbound shape Lemmy requires;
   - communities we host announce to the author's own instance too: **done 2026-10-06** (its server's shared inbox,