Votes a community relays count

Lemmy, PieFed and Mbin relay their members' votes, and the undoing of
them, inside the community's Announce; PrivaPub dropped them all as
unsupported (G-0003, the Lemmy scenario's expected failures). A relayed
Like, Dislike or Undo from a community a persona follows is now handled
as if its actor had sent it. The community vouches for what accounts on
its own server do and for what is done to its own posts, as Lemmy trusts
it (refetching every vote would not scale); a vote from elsewhere on
anything else is believed only once fetched from its own origin.
Moderation relayed the same way is still open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

docs/INTEROP.md

@@ -467,7 +467,7 @@ on a Page: pins live in `featured`, locks in `Lock`.
 | Gap | P | Client surface |
 |---|---|---|
 | `Dislike` and its `Undo`: a vote ledger per object (actor, ±1, activity, relaying group, time) | P1 | `favourites_count` = upvotes; own `privapub.vote{score, up, down, mine}`, `POST …/vote` |
-| Announces of activities other than Create (votes, moderation): trust the inner activity when the object's own group signed the Announce; refetching every vote does not scale. Keep the origin refetch for Create and Update. | P1 | — |
+| Announces of activities other than Create (votes, moderation): trust the inner activity when the object's own group signed the Announce; refetching every vote does not scale. Keep the origin refetch for Create and Update. Votes and their undoing **done** 2026-10-04 (`AnnounceHandler.Relayed`: trusted from the community's own server or on its own posts, otherwise fetched from the voter's origin); moderation still open | P1 | — |
 | Moderation state: removals (reason, by, at, cascade), locks, bans with `endTime`/`removeData`, featured, moderators, `Update{Group}` by a moderator | P1 | removed posts hidden plus `privapub.removed`; `privapub.locked` (replying answers 422); pins as `pinned=true` |
 | Link posts: keep `Link.href`, the thumbnail `image` and alt text; build the card (Lemmy sends no title or description for the link) | P1 | `Status.card` |
 | `ChatMessage` in and out (out only to Lemmy < 1.0 and Mbin; `Note` to everyone else) | P1 | `visibility: direct` |