fix(web-search): Kommentar für 2026er Auto-Injection + Code-Execution Beta-Header

- web_search_20260209 injected code_execution automatisch – nicht manuell hinzufügen
- Beta-Header code-execution-2025-08-25 hinzugefügt (für zukünftige Kompatibilität)

Services/AnthropicService.cs

@@ -1640,7 +1640,10 @@ public class AnthropicService
             tools.AddRange(allTools);
         }
         if (hasWebSearch)
+        {
             tools.Add(new { type = webSearchVersion, name = "web_search", max_uses = 5 });
+            // web_search_20260209: Code Execution wird von der API automatisch injected – NICHT manuell hinzufügen!
+        }
         payload["tools"] = tools;
         var effectiveChoice = (!planMode && toolChoice == "any" && iteration == 1) ? "any" : "auto";
         payload["tool_choice"] = new { type = effectiveChoice };
@@ -1695,7 +1698,7 @@ public class AnthropicService
         var client = _httpFactory.CreateClient();
         client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _token);
         client.DefaultRequestHeaders.Add("anthropic-version", "2023-06-01");
-        client.DefaultRequestHeaders.Add("anthropic-beta", "claude-code-20250219,oauth-2025-04-20");
+        client.DefaultRequestHeaders.Add("anthropic-beta", "claude-code-20250219,oauth-2025-04-20,code-execution-2025-08-25");
         client.DefaultRequestHeaders.Add("User-Agent", "claude-cli/2.1.2 (external, cli)");
         client.DefaultRequestHeaders.Add("x-app", "cli");
         client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));