T1: tests stop sharing state they don't own

- JobQueue takes an optional scope, so a test's worker leases and reaps only its own jobs.
- The dead-host delivery test runs alone (Exclusive), on its own jobs, and cleans up the
  breaker rows it trips; the breaker has tests of its own on unique hosts.
- Index and migration tests run alone: they drop indexes and rewrite every post.
- DomainBlocks.Load replaces reflection and a database-wide block in tests.
- Harness.Outgoing sees only deliveries queued since the harness started: Peer ports are
  reused within a run, which made the circle test flaky.
- Two pure-logic tests leave Mongo-gated classes, so CI runs them.

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

PrivaPub.Tests/Federation/ObjectRecordsTests.cs

@@ -0,0 +1,36 @@
+using PrivaPub.Federation.Objects;
+
+using System.Text.Json.Nodes;
+
+namespace PrivaPub.Tests.Federation
+{
+	public class ObjectRecordsTests
+	{
+		[Fact]
+		public void An_object_larger_than_the_cap_keeps_only_its_hash()
+		{
+			var big = new JsonObject { ["content"] = new string('x', ObjectRecords.MaxRawBytes + 1) };
+
+			var (text, hash, bytes, truncated) = ObjectRecords.Capture(big);
+
+			Assert.Null(text);
+			Assert.True(truncated);
+			Assert.True(bytes > ObjectRecords.MaxRawBytes);
+			Assert.Equal(64, hash.Length);
+		}
+
+		[Fact]
+		public void A_small_object_is_kept_whole_with_its_hash()
+		{
+			var small = new JsonObject { ["type"] = "Note", ["content"] = "hi" };
+
+			var (text, hash, bytes, truncated) = ObjectRecords.Capture(small);
+
+			Assert.Equal(small.ToJsonString(), text);
+			Assert.False(truncated);
+			Assert.Equal(text.Length, bytes);
+			Assert.Equal(64, hash.Length);
+			Assert.Equal(default, ObjectRecords.Capture(default));
+		}
+	}
+}