A sender's digest of its followers here is compared and mended

FEP-8fcf, received. When a delivery's Collection-Synchronization header digests the sender's followers on PrivaPub
otherwise than the personas following it, a job reads the list the header names (on the sender's origin, signed by the
instance actor): a follow the list leaves out ends, only when the list is the one the digest describes; a request it
lists is taken as accepted; a persona it lists that follows nothing there sends Undo{Follow}, as Mastodon does. Each
claiming delivery is compared once.

Checked live (scenarios/followsync.sh, now 15 checks): PrivaPub ends a follow Mastodon lost and undoes one only
Mastodon remembered.

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

docs/ROADMAP.md

@@ -672,8 +672,9 @@ it, raw where it doesn't.
   - re-run WebFinger on a rename;
   - inbound `Block`; `Add`/`Remove` of pins: **done 2026-10-05** (both ways, a community's pins too, the `featured`
     collection read with an account's counts; checked live against Mastodon);
-  - FEP-8fcf followers sync: sending **done 2026-10-06** (owner decision; the digest of a persona's followers on the
-    receiving server, and a signed roll-call listing only them; Mastodon mends both ways from it, checked live);
+  - FEP-8fcf followers sync: **done 2026-10-06** (owner decision; sent: the digest of a persona's followers on the
+    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`;
   - PeerTube reply rules and `ApproveReply`.