Account merge ledger: fix the first Soul pass (suspension carried into a memberless survivor, merged status terminal, standing at the desk door, linked accounts and write time, journalled grace intake, survivor weight on moved votes, one-hop alias, State token and database guards for overlapping merges, live-Postgres tests)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Bifrost.Web/Program.cs

@@ -856,7 +856,10 @@ app.MapPost("/auth/heimdall/complete", async (
                 held.Value.Value,
                 form?["code"].ToString(),
                 form?["pendingLinkId"].ToString(),
-                httpContext.User.FindFirstValue(BifrostClaimTypes.HeimdallAccountId),
+                // A folded or frozen account links nothing: the actor accessor's standing decides, not the raw claim.
+                (await httpContext.RequestServices.GetRequiredService<ICurrentBifrostActorAccessor>().GetAsync(cancellationToken)).Merge is null
+                    ? httpContext.User.FindFirstValue(BifrostClaimTypes.HeimdallAccountId)
+                    : null,
                 cancellationToken);
             if (step.Next is not null)
             {