fix(openai): Auto-Context, Tool-Result-Matching, Payload-Preview, leere Bubbles

- Auto-Context (Embedding-Suche) für OpenAI-Provider aktiviert: BuildAutoContextAsync
  auf internal static refactored und in StreamChat + ChatNonStreaming integriert
- Tool-Results mit Role="tool" (OpenAI-Konvention) werden in BuildHistoryFromDb
  jetzt korrekt erkannt (vorher nur Role="user"/Anthropic)
- Payload-Preview zeigt für OpenAI-Provider echtes API-Format (function-Wrapper,
  tool_choice:"auto", max_tokens, stream_options, extra_body)
- Tool-Input (Argumente) wird im SSE tool_end-Event mitgesendet (fehlte im OpenAI-Pfad)
- Leere Bubbles durch Whitespace-only Text nach </think>-Extraktion behoben
  (Trim in DB-Save, BuildHistoryFromDb und Frontend-Guard)
- History-Toggle-Bug: var→const in for-Loop (Block-Scoping für Closures),
  tool_result-Matching per data-tool-call-id statt blindes letztes Element
- Non-Streaming max_tokens für MiniMax auf 32768 + extra_body.reasoning_split

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Services/OpenAiService.cs

@@ -23,6 +23,7 @@ public class OpenAiService
     private readonly IHttpClientFactory _httpFactory;
     private readonly DatabaseService _db;
     private readonly ToolService _toolService;
+    private readonly VectorSearchService _vectorSearch;
 
     // Provider-Keys (statisch für ChatService.ResolveModelId)
     public static readonly HashSet<string> ProviderKeys = new() { "nvidia", "pollinations", "gemini", "openai", "minimax" };
@@ -36,7 +37,7 @@ public class OpenAiService
     /// Konvertiert Anthropic-Format Tool-Definitionen (input_schema) in OpenAI-Format (function/parameters).
     /// Single source of truth: ToolService.GetToolDefinitions()
     /// </summary>
-    private static List<object> ConvertTo_openAiToolDefs(object[] anthropicTools)
+    public static List<object> ConvertTo_openAiToolDefs(object[] anthropicTools)
     {
         var result = new List<object>();
         foreach (var tool in anthropicTools)
@@ -86,11 +87,12 @@ public class OpenAiService
 
     private readonly ServerSettingsService _settings;
 
-    public OpenAiService(IHttpClientFactory httpFactory, DatabaseService db, ToolService toolService, ServerSettingsService settings, string dataDir)
+    public OpenAiService(IHttpClientFactory httpFactory, DatabaseService db, ToolService toolService, ServerSettingsService settings, string dataDir, VectorSearchService vectorSearch = null)
     {
         _httpFactory = httpFactory;
         _db = db;
         _toolService = toolService;
+        _vectorSearch = vectorSearch;
         _settings = settings;
         _cacheFile = Path.Combine(dataDir, "models_cache.json");
         Providers = new Dictionary<string, (string BaseUrl, string ApiKey)>
@@ -295,6 +297,7 @@ public class OpenAiService
         string agentId = null,
         int maxIterations = 10,
         string apiKeyOverride = null,
+        bool useAutoContext = true,
         CancellationToken workCt = default,
         CancellationToken sseCt = default)
     {
@@ -328,6 +331,32 @@ public class OpenAiService
 
         try
         {
+            // ── Automatische Kontext-Injektion via Embedding-Suche ──
+            if (useAutoContext)
+            {
+                try
+                {
+                    var autoCtx = await AnthropicService.BuildAutoContextAsync(_vectorSearch, messages, chainId, agentId);
+                    if (autoCtx != null)
+                    {
+                        // Auto-Context an System-Prompt anhängen
+                        systemPromptText = (systemPromptText ?? "") + "\n" + autoCtx;
+                        await SseHelper.TryWriteSse(response, "auto_context", new { context = autoCtx }, sseCt);
+                        await _db.SaveMessage(new MessageRecord
+                        {
+                            ChainId = chainId,
+                            Role = "system",
+                            Type = "auto_context",
+                            Content = autoCtx
+                        });
+                    }
+                }
+                catch (Exception ex)
+                {
+                    Console.WriteLine($"[AutoContext/OpenAI] Error: {ex.Message}");
+                }
+            }
+
             var apiMessages = BuildApiMessages(systemPromptText, messages);
 
             // Agentic Loop
@@ -786,8 +815,8 @@ public class OpenAiService
                     });
                 }
 
-                // Text in DB speichern
-                var finalText = fullText.ToString();
+                // Text in DB speichern (Whitespace-only nach </think> ignorieren)
+                var finalText = fullText.ToString().Trim();
                 if (!string.IsNullOrEmpty(finalText))
                 {
                     await _db.SaveMessage(new MessageRecord
@@ -925,6 +954,7 @@ public class OpenAiService
                     {
                         name = tcName,
                         id = tcId,
+                        input = tcArgs.ToString(),
                         result = toolResult,
                         isError
                     }, sseCt);
@@ -1029,7 +1059,32 @@ public class OpenAiService
             Model = ctx.ModelId
         };
 
-        var apiMessages = BuildApiMessages(ctx.SystemPromptText, messages);
+        // ── Automatische Kontext-Injektion via Embedding-Suche ──
+        var systemPromptText = ctx.SystemPromptText;
+        if (ctx.Agent?.UseAutoContext ?? true)
+        {
+            try
+            {
+                var autoCtx = await AnthropicService.BuildAutoContextAsync(_vectorSearch, messages, ctx.ChainId, ctx.AgentId);
+                if (autoCtx != null)
+                {
+                    systemPromptText = (systemPromptText ?? "") + "\n" + autoCtx;
+                    await _db.SaveMessage(new MessageRecord
+                    {
+                        ChainId = ctx.ChainId,
+                        Role = "system",
+                        Type = "auto_context",
+                        Content = autoCtx
+                    });
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"[AutoContext/OpenAI-NonStreaming] Error: {ex.Message}");
+            }
+        }
+
+        var apiMessages = BuildApiMessages(systemPromptText, messages);
 
         try
         {
@@ -1039,12 +1094,13 @@ public class OpenAiService
                 onIteration?.Invoke(iterations);
 
                 var client = CreateClient(providerConfig.ApiKey);
+                var maxTokens = provider == "minimax" ? 32768 : 16384;
                 var payload = new Dictionary<string, object>
                 {
                     ["model"] = modelId,
                     ["messages"] = apiMessages,
                     ["stream"] = false,
-                    ["max_tokens"] = 16384,
+                    ["max_tokens"] = maxTokens,
                     ["tools"] = _openAiToolDefs,
                     ["tool_choice"] = "auto"
                 };
@@ -1052,6 +1108,9 @@ public class OpenAiService
                 if (provider == "nvidia" && IsNvidiaThinkingModel(modelId))
                     payload["chat_template_kwargs"] = new { thinking = true };
 
+                if (provider == "minimax")
+                    payload["extra_body"] = new { reasoning_split = true };
+
                 var jsonPayload = JsonSerializer.Serialize(payload);
                 var httpContent = new StringContent(jsonPayload, Encoding.UTF8, "application/json");
 
@@ -1364,7 +1423,7 @@ public class OpenAiService
     /// <summary>
     /// Konvertiert Anthropic-Format Messages in OpenAI-kompatibles Format.
     /// </summary>
-    private static List<object> BuildApiMessages(string systemPromptText, List<object> messages)
+    public static List<object> BuildApiMessages(string systemPromptText, List<object> messages)
     {
         var apiMessages = new List<object>();
         if (!string.IsNullOrEmpty(systemPromptText))