fix: Tag-Feld für Sub-Agent-Messages – verhindert API 400 bei tool_use ohne tool_result

- MessageRecord: neues Tag-Feld (null=normal, preparer/review/finalizer=Sub-Agent)
- DatabaseService: Migration tag-Spalte, INSERT-Statements erweitert
- AnthropicService: RunAgentChat setzt Tag=agentType bei allen 4 SaveMessage-Aufrufen
- ChatService: BuildHistoryFromDb filtert getaggte Messages aus API-History

Sub-Agent-Messages bleiben in der DB (Frontend-Anzeige), werden aber
nie an die Claude API geschickt – löst das Problem für Preparer,
Review und Finalizer gleichermaßen.

Models/MessageRecord.cs

@@ -13,6 +13,7 @@ public class MessageRecord
     public int Iteration { get; set; }       // welche Loop-Iteration
     public int AttachmentCount { get; set; } // Anzahl angehängter Dateien
     public string AttachmentNames { get; set; } // JSON-Array mit Dateinamen
+    public string Tag { get; set; }           // null = normal, "preparer"/"review"/"finalizer" = Sub-Agent-Message
     public bool IsMarked { get; set; }       // als wichtig markiert
     public string DeletedOn { get; set; }    // null = aktiv, sonst Zeitstempel der Löschung
     public string CreatedAt { get; set; }

Services/AnthropicService.cs

@@ -691,7 +691,8 @@ public class AnthropicService
                         Iteration = baseIterations + iterations,
                         Role = "assistant",
                         Type = "text",
-                        Content = $"[{tag}: {agentName}] {text}"
+                        Content = $"[{tag}: {agentName}] {text}",
+                        Tag = agentType
                     });
                 }
                 else if (blockType == "tool_use")
@@ -718,7 +719,8 @@ public class AnthropicService
                         Type = "tool_use",
                         Content = toolInput.GetRawText(),
                         ToolName = toolName,
-                        ToolCallId = toolId
+                        ToolCallId = toolId,
+                        Tag = agentType
                     });
 
                     string toolResult;
@@ -748,7 +750,8 @@ public class AnthropicService
                         Content = toolResult,
                         ToolName = toolName,
                         ToolCallId = toolId,
-                        IsError = isError
+                        IsError = isError,
+                        Tag = agentType
                     });
                 }
                 else if (blockType == "web_search_tool_result")
@@ -779,7 +782,8 @@ public class AnthropicService
                             Iteration = baseIterations + iterations,
                             Role = "assistant",
                             Type = "web_search_result",
-                            Content = JsonSerializer.Serialize(sources)
+                            Content = JsonSerializer.Serialize(sources),
+                            Tag = agentType
                         });
                     }
                 }

Services/ChatService.cs

@@ -329,7 +329,9 @@ Bitte speichere es in die Datei products.json im Workspace.
             var chain = chainsList[i];
             isLastChain = (i == chainsList.Count - 1);
 
-            var msgs = (await _db.GetChainMessages(chain.ChainId)).ToList();
+            var msgs = (await _db.GetChainMessages(chain.ChainId))
+                .Where(m => string.IsNullOrEmpty(m.Tag)) // Sub-Agent-Messages (preparer/review/finalizer) aus API-History ausfiltern
+                .ToList();
 
             // Letzte User-Message-ID der letzten Chain merken (für Attachments)
             if (isLastChain || i == fullChainStartIndex)

Services/DatabaseService.cs

@@ -181,6 +181,7 @@ public class DatabaseService
         TryAddColumn(conn, "agents", "allow_user_choice", "INTEGER NOT NULL DEFAULT 1");
         TryAddColumn(conn, "chains", "plan_mode", "INTEGER NOT NULL DEFAULT 0");
         TryAddColumn(conn, "sessions", "preparer_agent_id", "TEXT");
+        TryAddColumn(conn, "messages", "tag", "TEXT");
 
         conn.Execute(@"
             CREATE TABLE IF NOT EXISTS agent_skills (
@@ -629,8 +630,8 @@ public class DatabaseService
         using var conn = CreateConnection();
         record.CreatedAt = DateTime.UtcNow.ToString("o");
         return await conn.ExecuteScalarAsync<long>(@"
-            INSERT INTO messages (chain_id, role, type, content, tool_name, tool_call_id, is_error, iteration, attachment_count, created_at)
-            VALUES (@ChainId, @Role, @Type, @Content, @ToolName, @ToolCallId, @IsError, @Iteration, @AttachmentCount, @CreatedAt);
+            INSERT INTO messages (chain_id, role, type, content, tool_name, tool_call_id, is_error, iteration, attachment_count, tag, created_at)
+            VALUES (@ChainId, @Role, @Type, @Content, @ToolName, @ToolCallId, @IsError, @Iteration, @AttachmentCount, @Tag, @CreatedAt);
             SELECT last_insert_rowid();
         ", record);
     }
@@ -651,8 +652,8 @@ public class DatabaseService
             record.AttachmentNames = System.Text.Json.JsonSerializer.Serialize(names);
         }
         var messageId = await conn.ExecuteScalarAsync<long>(@"
-            INSERT INTO messages (chain_id, role, type, content, tool_name, tool_call_id, is_error, iteration, attachment_count, attachment_names, created_at)
-            VALUES (@ChainId, @Role, @Type, @Content, @ToolName, @ToolCallId, @IsError, @Iteration, @AttachmentCount, @AttachmentNames, @CreatedAt);
+            INSERT INTO messages (chain_id, role, type, content, tool_name, tool_call_id, is_error, iteration, attachment_count, attachment_names, tag, created_at)
+            VALUES (@ChainId, @Role, @Type, @Content, @ToolName, @ToolCallId, @IsError, @Iteration, @AttachmentCount, @AttachmentNames, @Tag, @CreatedAt);
             SELECT last_insert_rowid();
         ", record, tx);