Public threads name their replies and context

Owner decision of 2026-10-06: a persona's public or unlisted post outside any group names its replies
(…/scribbles/{id}/replies) and its conversation's context (FEP-7888), the root's …/context that a reply inherits from
its parent, ours or another server's. Both list only the public and unlisted posts PrivaPub holds; followers-only,
circle, direct and local-only posts name neither and their collections answer 404. Checked live: opening alice's
thread on Mastodon finds carol's reply, which nobody there follows (scenarios/threads.sh).

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

docs/ROADMAP.md

@@ -654,7 +654,8 @@ it, raw where it doesn't.
     reads at most 5 pages and 100 posts per job, signed by the instance actor, and stores what it lacks through
     `StoreContext` (public and unlisted only, the author checked against its origin);
   - group by the root post;
-  - publish our own `context` and a paged `replies`.
+  - publish our own `context` and `replies`: **done 2026-10-06** (owner decision; public and unlisted posts outside groups,
+    public and unlisted replies only; Mastodon finds a thread's replies through them, checked live).
 - **Lemmy, PieFed and Mbin:**
   - the moderation set: removals, locks, bans (**done 2026-10-05**, relayed by the community: a lock refuses replies, a
     ban of a persona refuses its posts there and shows as `blocked_by`), featured, moderators, `Warn`, `Resolve`;