E2E: a known gap skips its test, and reactions start clean

A test whose failure an open gap of the town's gaps.json names (a peer's
own bug, such as Misskey keeping its renote count after our Undo, G-0005)
is now skipped with the gap's id instead of failing the run; the report
still counts the cell an expected failure. The reaction test starts by
withdrawing a reaction a run cut short left behind, so one failure no
longer makes the next run fail too.

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

tests/e2e/Support/Results.cs

@@ -1,13 +1,27 @@
 using System.Text.Json;
+using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
 
 namespace decePubClient.E2E.Support
 {
 	// Each render and action test is also a cell of the town's matrix, appended to the pasture's out/client.jsonl in the
-	// cell format town.sh check writes, so report.html shows decePub next to the servers.
+	// cell format town.sh check writes, so report.html shows decePub next to the servers. A failure that an open gap of the
+	// town's gaps.json names (a peer's own bug, say) is skipped with the gap's id rather than failed, as the report counts
+	// it an expected failure.
 	public static class Results
 	{
 		static readonly object Gate = new();
 		static readonly string FilePath = Path.Combine(Pasture.Root, "out", "client.jsonl");
+		static readonly Lazy<JsonArray> Gaps = new(() => JsonNode.Parse(File.ReadAllText(Path.Combine(Pasture.Root, "town", "gaps.json")))!.AsArray());
+
+		// the open gap whose match (regular expressions over the cell's fields) fits this cell, if any
+		static string KnownGap(string feature, string origin)
+		{
+			var fields = new Dictionary<string, string> { ["feature"] = feature, ["origin"] = origin, ["observer"] = "decepub" };
+			return Gaps.Value.Where(g => g?["status"]?.GetValue<string>() != "closed" && g?["match"] is JsonObject)
+				.FirstOrDefault(g => g!["match"]!.AsObject().All(m => Regex.IsMatch(fields.GetValueOrDefault(m.Key, ""), $"^(?:{m.Value!.GetValue<string>()})$")))
+				?["id"]?.GetValue<string>();
+		}
 
 		public static async Task Cell(string feature, string origin, string reference, Func<Task> test) =>
 			await Cell(feature, origin, reference, test, page: null);
@@ -27,6 +41,8 @@ namespace decePubClient.E2E.Support
 				got = e.Message.Length > 400 ? e.Message[..400] : e.Message;
 				if (page is not null)
 					await SignIn.Evidence(page, $"{feature}-{origin}-{reference}".Replace('/', '_').Replace('@', '_'));
+				if (KnownGap(feature, origin) is { } gap)
+					Assert.Skip($"known gap {gap}: {got}");
 				throw;
 			}
 			finally