FakeClaude, test per area e renderer diviso in due file

- tests/FakeClaude: eseguibile finto 'claude' configurabile con variabili
  d'ambiente (registro di argomenti/cwd/stdin, output, exit code, ritardo),
  con le prove FK-01…FK-05.
- Test organizzati per livello (Gui/, Process/, Support/) e struttura
  descritta in TESTING.md.
- MarkdownView: la parte sulle immagini passa in MarkdownView.Images.cs
  (partial), senza cambiare il comportamento.

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

tests/FakeClaude/Program.cs

@@ -0,0 +1,15 @@
+using System.Text.Json;
+
+// Configurazione e formato del registro: docs/TESTING.md → FakeClaude.
+var stdin = Console.In.ReadToEnd(); // resta in attesa finché il chiamante non chiude stdin
+
+if (Environment.GetEnvironmentVariable("FAKE_CLAUDE_LOG") is { Length: > 0 } log)
+    File.AppendAllText(log, JsonSerializer.Serialize(new { args, cwd = Directory.GetCurrentDirectory(), stdin }) + "\n");
+
+if (int.TryParse(Environment.GetEnvironmentVariable("FAKE_CLAUDE_DELAY_MS"), out var delay) && delay > 0)
+    Thread.Sleep(delay);
+
+if (Environment.GetEnvironmentVariable("FAKE_CLAUDE_OUT") is { } o) Console.Out.Write(o);
+if (Environment.GetEnvironmentVariable("FAKE_CLAUDE_ERR") is { } e) Console.Error.Write(e);
+
+return int.TryParse(Environment.GetEnvironmentVariable("FAKE_CLAUDE_EXIT"), out var code) ? code : 0;