A remote thread brings the replies that never reached us

The context of a remote post showed only what PrivaPub happened to hold:
replies from servers nobody here follows were never seen, and only the
ancestors were ever fetched. Now a persona opening a public remote thread
queues FetchReplies for the post and its root, at most once an hour each.

The job reads the thread's own collection first (FEP-7888 `context`, which
Mastodon 4.5+ serves with every reply at any depth; posts or, as FEP-f228
allows, the activities that made them), and otherwise the post's `replies`
(PeerTube's `comments`) and the replies' own, two levels down. At most 5
pages and 100 posts a job, signed by the instance actor, never a persona;
each post is fetched from its own origin and stored through StoreContext,
so only public and unlisted ones are kept.

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

PrivaPub/Infrastructure/Statistics/InteractionLedger.cs

@@ -44,7 +44,7 @@ namespace PrivaPub.Infrastructure.Statistics
 			SingleReader = false
 		});
 		static readonly TimeSpan TouchInterval = TimeSpan.FromHours(1);
-		static readonly HashSet<string> TouchingPurposes = new(StringComparer.Ordinal) { "actor", "key", "object", "webfinger", "context" };
+		static readonly HashSet<string> TouchingPurposes = new(StringComparer.Ordinal) { "actor", "key", "object", "webfinger", "context", "replies" };
 
 		readonly InteractionSalts _salts;
 		readonly IOptionsMonitor<StatisticsOptions> _options;