Following an account brings its earlier posts to its profile

Once a follow holds, OutboxBackfill reads the account's latest public posts from its outbox's first page (twenty at
most, once a day) and keeps them as any fetched post: its profile shows them at once instead of only what it posts from
then on. Homes still get only what arrives afterwards, as on Mastodon. Announces and other servers' objects in the
outbox are left out. Checked live against Mastodon (scenarios/pins.sh, now 9 checks).

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

FEDERATION.md

@@ -143,7 +143,7 @@ Received:
 | Activity | Effect |
 |---|---|
 | `Follow` | follows an avatar or community; `Accept` is sent unless the community approves members by hand |
-| `Accept{Follow}`, `Reject{Follow}` | completes or ends a follow an avatar requested |
+| `Accept{Follow}`, `Reject{Follow}` | completes or ends a follow an avatar requested; once a follow holds, the account's latest public posts are read from its outbox's first page (twenty at most, once a day), so its profile is not empty; homes get only what arrives from then on |
 | `Accept{Join}`, `Reject{Join}` | from the event's server: a persona's participation in the event is accepted or refused |
 | `Undo{Follow, Like, Announce}` | reverses it |
 | `Create{Note, Article, Page, Question, Video, Audio, Event, ChatMessage, …}` | stored when a local avatar follows the author, is addressed or mentioned, when it replies to a local post, or when it is addressed to a community the author follows (a persona is addressed by its actor id or by its profile page, as Mbin addresses its private messages); a public parent is fetched to complete the thread |