Edit history from formerRepresentations

Pleroma and Akkoma send a post's earlier versions with it. A post PrivaPub first meets after its edits now has its
history, and an edit that carries them brings the versions missed in between; each is read as the post itself is. The
Akkoma scenario checks a post fetched after two edits by an account no persona follows.

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

docs/ROADMAP.md

@@ -677,7 +677,8 @@ it, raw where it doesn't.
     receiving server, and a signed roll-call listing only them; honoured: a sender's digest of its followers here,
     mended from its list; checked live against Mastodon, all four ways a follow can be lost);
   - `indexable`/`discoverable`/`searchableBy`;
-  - edit history from `formerRepresentations`;
+  - edit history from `formerRepresentations`: **done 2026-10-06** (Pleroma's and Akkoma's earlier versions, for a post
+    met after its edits and for the edits missed in between);
   - PeerTube reply rules and `ApproveReply`.
 - **Events:** structured RSVP (`Join`/`Leave` with stable ids): **done 2026-10-05** (owner decision above), checked live
   against Mobilizon.