NodeInfo is read as Mobilizon serves it

Mobilizon sends its NodeInfo as `application/json; profile=http://…#` with the URL unquoted, which .NET cannot parse,
so the document was refused for its content type and the server never described; and it names its software
"Mobilizon" where NodeInfo wants lower case. The media type is now read from the raw header when the parsed one is
missing, and software names are lowercased, so one software is counted under one name.

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

PrivaPub/Infrastructure/Http/FederationHttp.cs

@@ -218,7 +218,7 @@ namespace PrivaPub.Infrastructure.Http
 						exchange.Refused(StatusReason(response));
 						return items;
 					}
-					var mediaType = response.Content.Headers.ContentType?.MediaType;
+					var mediaType = MediaType(response.Content.Headers);
 					if (mediaType == default || !JsonMediaTypes.Contains(mediaType, StringComparer.OrdinalIgnoreCase))
 					{
 						exchange.Refused("content-type");
@@ -356,7 +356,7 @@ namespace PrivaPub.Infrastructure.Http
 						return Refuse(negativeKey, url, $"status {(int)response.StatusCode}", exchange, StatusReason(response),
 							transient: (int)response.StatusCode is >= 500 or 429 or 408);
 
-					var mediaType = response.Content.Headers.ContentType?.MediaType;
+					var mediaType = MediaType(response.Content.Headers);
 					if (mediaType == default || !JsonMediaTypes.Contains(mediaType, StringComparer.OrdinalIgnoreCase))
 						return Refuse(negativeKey, url, $"content type '{mediaType}'", exchange, "content-type");
 					if (response.Content.Headers.ContentLength > MaxResponseBytes)
@@ -629,6 +629,11 @@ namespace PrivaPub.Infrastructure.Http
 
 		static string NegativeKey(Uri target) => "federation-http:refused:" + target.AbsoluteUri;
 
+		// the media type, also from a header .NET cannot parse: Mobilizon's NodeInfo leaves its profile URL unquoted
+		static string MediaType(System.Net.Http.Headers.HttpContentHeaders headers) =>
+			headers.ContentType?.MediaType
+			?? (headers.NonValidated.TryGetValues("Content-Type", out var raw) ? raw.ToString().Split(';')[0].Trim() : default);
+
 		sealed record Refusal(bool Transient, int Status);
 
 		FetchedJson Refuse(string negativeKey, string url, string reason, Exchange exchange, string code, bool transient = false)