Pasture: scenarios run again on the same pasture, and Mastodon's threads

GoToSocial's and Mastodon's scenarios passed once on a fresh pasture only:
their locked follows ended followed, so a second run found no request to
reject, and Mastodon's ended with mastouser blocking alice_masto, so every
follow after it was rejected. Each now unfollows first, and Mastodon's
undoes its block (checking that its Undo{Block} reaches our blocked_by) and
its lock; a run cut short is undone at the start.

Mastodon's scenario also checks the thread backfill live: a reply by an
account nobody here follows is never delivered, and joins the thread once
alice_masto opens it, read from Mastodon's FEP-7888 context.

interop.sh keeps the results of the peers it does not run, so the report
merges a partial rerun. All seven scenarios: 276 pass, 0 fail, 1 expected
(Lemmy moderation, P7).

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

docs/INTEROP.md

@@ -151,10 +151,13 @@ Priorities, used throughout:
 | Publish `context` and a paged `replies` | P2 | — |
 | `FeatureRequest`: send `Reject` (or implement FEP-7aa9) | P3 | — |
 
-**Pasture evidence (2026-10-03, Mastodon v4.7.3, `tools/pasture/scenarios/mastodon.sh`):** 49 checks pass. They cover:
+**Pasture evidence (2026-10-05, Mastodon v4.7.3, `tools/pasture/scenarios/mastodon.sh`):** 56 checks pass, and the
+scenario can be run again on the same pasture (it undoes the lock and the block it leaves). They cover:
 - discovery, follows and locked follows both ways;
 - public, CW and followers-only posts (the last answering 404 unsigned);
 - replies threading both ways;
+- a thread completed from Mastodon's FEP-7888 `context`: a reply by an account nobody here follows, never delivered,
+  joins the thread once a persona opens it;
 - likes, boosts and their undos both ways, with counts;
 - DMs both ways;
 - polls and votes both ways;
@@ -164,7 +167,7 @@ Priorities, used throughout:
 - deletes both ways, ours answering 410;
 - a Flag reaching Mastodon's moderators from the instance actor;
 - a circle request held for its owner and approved;
-- unfollow and block;
+- unfollow, block and unblock both ways (Mastodon's block and its undo reach our `blocked_by`);
 - statistics naming `mastodon.test` as mastodon with no account names.
 
 Findings:
@@ -239,7 +242,8 @@ Findings:
 
 **Pasture evidence (2026-10-03, GoToSocial 0.22.1, `tools/pasture/scenarios/gts.sh`):** 37 checks pass, three runs in a
 row. That is the original 33 plus four on statistics: described as gotosocial, inbound and outbound traffic counted,
-no account named. Since 2026-10-04 (v1.19.0) circle posts reach a GoToSocial member too. GoToSocial files a post for
+no account named. On 2026-10-05 the scenario runs 55 checks, all passing, and can be run again on the same pasture (the
+locked persona loses its follower first). Since 2026-10-04 (v1.19.0) circle posts reach a GoToSocial member too. GoToSocial files a post for
 neither the public nor the author's followers as a direct message, like our DMs, and shows it only to the accounts it
 mentions. Being in `cc` stored it but left it invisible, so each member's copy also mentions that member silently.
 Such posts are then found in the member's conversations, never by a search on their URI.