Our @context stays JSON-LD 1.0, and a 500 no longer takes a host out

The proof term added with integrity proofs had a @graph container, which only JSON-LD 1.1 knows: Smithereen's reader
refused every document carrying our context with a 500. Those 500s, retried, then put Smithereen's host in quarantine
for an hour, and every delivery to it waited. Proofs are canonicalised as JSON (JCS), so the term loses nothing as a
plain id; a test keeps every term within 1.0. Only an unreachable host, a timeout or a gateway's 502, 503 or 504 now
counts against a host: a 500 is the server failing on that one activity, retried on its own.

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

FEDERATION.md

@@ -391,7 +391,8 @@ Posts with a location (shown to nearby users of this server) never leave the ser
 - **Delivery.** An activity goes once to each server, to its shared inbox when the server has one, whoever there it
   follows, names or answers (a circle post excepted: each member's copy names that member). Failed deliveries are
   retried with Mastodon's backoff (16 attempts). A host that keeps failing is paused,
-  starting at an hour and growing to a week. A server can also take a Follow (202) and drop it afterwards, as Pleroma
+  starting at an hour and growing to a week: unreachable, timing out, or a gateway answering 502, 503 or 504. A 500 is
+  the server failing on that one activity, retried on its own while its other deliveries go on. A server can also take a Follow (202) and drop it afterwards, as Pleroma
   does when it cannot yet fetch our actor, so a follow request still unanswered is sent again, same activity, when the
   persona follows once more, at most once an hour.