System prompt: build from agent persona/instructions, store in chain, remove UI textarea

Endpoints/ChatEndpoint.cs

@@ -75,6 +75,15 @@ public static class ChatEndpoint
         res.Headers["Cache-Control"] = "no-cache";
         res.Headers["Connection"] = "keep-alive";
 
+        var promptParts = new List<string>();
+        promptParts.Add($"Du bist {agent.Name}.");
+        if (!string.IsNullOrWhiteSpace(agent.Persona))
+            promptParts.Add($"## Persona\n{agent.Persona}");
+        if (!string.IsNullOrWhiteSpace(agent.Instructions))
+            promptParts.Add($"## Instructions\n{agent.Instructions}");
+
+        var systemPromptText = string.Join("\n\n", promptParts);
+
         var chainId = Guid.NewGuid().ToString("N");
 
         await db.CreateChain(new ChainRecord
@@ -83,7 +92,7 @@ public static class ChatEndpoint
             SessionId = sessionId,
             AgentId = agent.AgentId,
             Model = modelId,
-            SystemPrompt = body.SystemPrompt
+            SystemPrompt = systemPromptText
         });
 
         // Session-Timestamp aktualisieren
@@ -107,23 +116,10 @@ public static class ChatEndpoint
             });
         }
 
-        var systemPrompt = new List<object>();
-
-        // Agent Persona
-        if (!string.IsNullOrWhiteSpace(agent.Persona))
-            systemPrompt.Add(new { type = "text", text = agent.Persona });
-
-        // Agent Instructions
-        if (!string.IsNullOrWhiteSpace(agent.Instructions))
-            systemPrompt.Add(new { type = "text", text = agent.Instructions });
-
-        // Zusätzlicher System Prompt aus dem UI
-        if (!string.IsNullOrWhiteSpace(body.SystemPrompt))
-            systemPrompt.Add(new { type = "text", text = body.SystemPrompt });
-
-        // Fallback wenn gar nix gesetzt
-        if (systemPrompt.Count == 0)
-            systemPrompt.Add(new { type = "text", text = "Du bist ein hilfreicher Assistent." });
+        var systemPrompt = new List<object>
+        {
+            new { type = "text", text = systemPromptText }
+        };
 
         var anthropic = new AnthropicService(httpFactory, token, toolService, db);
         await anthropic.StreamChat(res, modelId, systemPrompt, messages, chainId);