T8: inbox gaps, jobs, migrations and pages; a deleted remote account's posts are hidden

Owner decision (2026-10-03, "A remote account deletes itself"): its posts are kept but
hidden everywhere.
- Post.AuthorGone (additive bool). DeleteHandler's actor-delete branch sets it on every
  post whose ActorURI is the actor (one update-many), besides dropping its follows and
  timeline rows as before. RemotePosts.Build sets it on a post stored later for an
  account already marked Deleted.
- One rule in VisibilityPolicy: IsShown (not deleted, author not gone), IsPublic and
  CanSee exclude AuthorGone, plus Shown(post) for loaded posts.
- Lookups by id answer 404 through CanSee (statuses/:id and every sub-route, context,
  bookmarks, favourites, polls, reactions, search); provenance, account statuses,
  home/public/tag timelines, notifications, conversations, reblogged_by, the clientapi
  home and post/DM lists, a community's outbox and our Announces filter on IsShown or
  IsPublic; the Mastodon mapper never renders a hidden post or a boost of one.

Tests (30 new):
- AuthorGoneTests: the rule, the handler (posts kept, boosts included, follows and rows
  gone), a post fetched after the delete, and 20 Mastodon/ActivityPub lookups over HTTP
  seen before and hidden after.
- InboxGapTests: actor Update refresh (name, sanitised summary, key rotation in place
  and to a new key id) even with an older `updated`; Undo{Follow} by activity id and by
  object; Reject of our QuoteRequest (and a stranger's ignored); group-wrapped
  Announce{Like} and Announce{Undo{Like}}; a locked persona's pending follow,
  FollowRequest notification, and Decide accepting and rejecting with the original Follow.
- JobHandlerTests: AncestorsJobHandler up to its depth limit; PollRefreshJob and
  PollCloseJob (local and remote polls); InstanceDescriber from a peer's NodeInfo and
  the weekly dedupe through ObjectRecords; LinkPreviews for public posts only;
  DeliveryJobHandler outcomes (2xx, 404/410, 429/503 with Retry-After in seconds and as
  a date, 5xx) and a signature and Digest the peer can verify; MediaJanitor.Sweep;
  OAuthPruner.Prune.
- MigrationTests: _003, _004, _006 and _007 on seeded rows.
- PublicPagesTests: /@user and /@user/{id} (visibility, junk ids, exact CSP,
  Referrer-Policy and nosniff), circle 404, community page, the instance actor,
  ActivityPub redirects, and markup escaped in posts, titles and bios.

Production changes besides the rule:
- LinkPreviews.Handle re-checks that a post is still shown and public (the rule
  Wanted applies) before fetching anything; before, only enqueueing checked it.
- The legacy /clientapi post and DM lists no longer return soft-deleted posts.
- MediaJanitor.Sweep and OAuthPruner.Prune are the loop bodies, now public and tested.
- InstanceDescriber.Address: a protected virtual identity seam so a test can point
  the https NodeInfo addresses at a plain-http peer; production behaviour unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -314,7 +314,7 @@ namespace PrivaPub.Federation.Controllers
 		async Task<JsonObject> AnnounceFor(PostEntity reblog, CancellationToken token)
 		{
 			var original = await _dbEntities.Posts.MatchID(reblog.ReblogOfPostId).ExecuteFirstAsync(token);
-			if (original == default || original.DeletedAt.HasValue)
+			if (!VisibilityPolicy.Shown(original))
 				return default;
 			return new JsonObject
 			{

PrivaPub/Federation/Inbox/Handlers/DeleteHandler.cs

@@ -70,6 +70,7 @@ namespace PrivaPub.Federation.Inbox.Handlers
 				}
 				await DB.Default.DeleteAsync<Following>(f => f.TargetActorURI == actor.ActorURI);
 				await DB.Default.DeleteAsync<TimelineEntry>(e => e.AuthorAccountId == actor.ID);
+				await DB.Default.Update<PostEntity>().Match(p => p.ActorURI == actor.ActorURI).Modify(p => p.AuthorGone, true).ExecuteAsync(token);
 				return;
 			}
 

PrivaPub/Federation/Inbox/RemotePosts.cs

@@ -102,6 +102,7 @@ namespace PrivaPub.Federation.Inbox
 				AnsweringToPostId = parent?.ID,
 				InReplyToAccountId = parent?.AuthorAccountId ?? parent?.GroupUserId,
 				IsFederatedCopy = true,
+				AuthorGone = author.AccountState == AvatarAccountState.Deleted,
 				CreationDate = note.Published,
 				UpdateDate = note.Updated ?? note.Published,
 				EditedAt = note.Updated

PrivaPub/Federation/Objects/InstanceDescriber.cs

@@ -30,15 +30,18 @@ namespace PrivaPub.Federation.Objects
 		{
 			var host = job.Payload;
 			using var scope = HttpScope.For("nodeinfo");
-			using var links = await _http.GetJson($"https://{host}/.well-known/nodeinfo", "application/json", sign: default, token);
+			using var links = await _http.GetJson(Address($"https://{host}/.well-known/nodeinfo"), "application/json", sign: default, token);
 			var href = links == default ? default : Schemas.Select(schema => LinkFor(links.Root, schema)).FirstOrDefault(link => link != default);
 			if (href == default)
 				return await Described(host, default, "no NodeInfo", token);
 
-			using var nodeInfo = await _http.GetJson(href, "application/json", sign: default, token);
+			using var nodeInfo = await _http.GetJson(Address(href), "application/json", sign: default, token);
 			return nodeInfo == default ? await Described(host, default, "NodeInfo unreadable", token) : await Described(host, nodeInfo.Root, default, token);
 		}
 
+		//where an https address is fetched from: itself, except in tests, which point it at a plain-http peer
+		protected virtual string Address(string url) => url;
+
 		static async Task<JobOutcome> Described(string host, JsonElement? nodeInfo, string error, CancellationToken token)
 		{
 			var update = DB.Default.Update<RemoteInstance>()