PieFed joins the pasture; the instance actor answers at the root

PieFed 1.7.17 (dockurr's image of the release) runs in the pasture with its
Celery worker on the shared Postgres and Redis, and scenarios/piefed.sh
checks it both ways: 29 checks, communities, titled threads, comments, votes
up and down, a community poll and a vote in it, private messages, a
moderator's lock, unlock and removal, the unfollow and statistics.

What it showed:
- PieFed sends a community's announces to the inbox of the Application at a
  peer's root (as Lemmy serves its site actor) and to /inbox otherwise.
  PrivaPub answered 404 at its root, so every announce went to an /inbox it
  does not have. The instance actor now answers at / for ActivityPub
  requests, unsigned under SecureMode as at its own address.
- PieFed keeps serving a thread its moderator removed, so the removal could
  never be checked against the post's origin. A community on the post's own
  server now speaks for it; one elsewhere still waits for the origin to say
  the post is gone.

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

tools/pasture/run.sh

@@ -4,7 +4,7 @@
 # API at http://127.0.0.1:6971 ($PASTURE_PORT), every site at https://<name>.test:6443 (curl --resolve <name>.test:6443:127.0.0.1 -k).
 # usage: tools/pasture/run.sh up [peer...] | add <peer...> | down [--purge] | logs <name> | ps | stats
 #   up starts everything afresh (PrivaPub republished, Mongo empty); add starts more peers next to a running pasture.
-#   peers: gts (default), mastodon, misskey, sharkey, akkoma, lemmy, decepub
+#   peers: gts (default), mastodon, misskey, sharkey, akkoma, lemmy, decepub, and every other file in peers/
 set -euo pipefail
 . "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/lib/pasture.sh"