Implement Skills feature: filesystem-based skills with agent assignment

- Add SkillService: scans data/skills/ directory, parses _meta.json and SKILL.md frontmatter
- Add SkillEndpoint: REST API for listing skills and managing agent-skill assignments
- Add agent_skills DB table for agent-to-skill mapping (only relation in DB, skills live on filesystem)
- Extend SystemPromptBuilder: inject assigned skills' SKILL.md content into system prompt
- Extend ChatEndpoint + SessionEndpoint: load agent skills and pass to prompt builder
- Frontend: skill checkboxes in agent form, API functions for skill management
- Add form.css styling for skill list items

Endpoints/ChatEndpoint.cs

@@ -23,7 +23,7 @@ public static class ChatEndpoint
         app.MapPost("/api/chat", HandleChat);
     }
 
-    private static async Task HandleChat(HttpRequest req, HttpResponse res, IHttpClientFactory httpFactory, IConfiguration config, ToolService toolService, DatabaseService db, StreamingTracker streamingTracker, MemoryService memoryService, CancellationToken cancellationToken)
+    private static async Task HandleChat(HttpRequest req, HttpResponse res, IHttpClientFactory httpFactory, IConfiguration config, ToolService toolService, DatabaseService db, StreamingTracker streamingTracker, MemoryService memoryService, SkillService skillService, CancellationToken cancellationToken)
     {
         var body = await JsonSerializer.DeserializeAsync<ChatRequest>(req.Body);
         if (body == null || body.Messages == null || body.Messages.Count == 0)
@@ -80,7 +80,8 @@ public static class ChatEndpoint
         var markedMessages = await db.GetMarkedMessages(sessionId);
         var agentMemoryDir = memoryService.GetAgentMemoryDir(agent.AgentId);
         var dataDir = memoryService.DataDir;
-        var systemPromptText = SystemPromptBuilder.Build(agent, session, markedMessages, memoryService, agentMemoryDir, dataDir);
+        var agentSkills = await db.GetAgentSkills(agent.AgentId);
+        var systemPromptText = SystemPromptBuilder.Build(agent, session, markedMessages, memoryService, agentMemoryDir, dataDir, agentSkills, skillService);
 
         var chainId = Guid.NewGuid().ToString("N");
 

Endpoints/SessionEndpoint.cs

@@ -91,7 +91,7 @@ public static class SessionEndpoint
         ctx.Response.StatusCode = 204;
     }
 
-    private static async Task HandleSystemPrompt(HttpContext ctx, DatabaseService db, MemoryService memoryService)
+    private static async Task HandleSystemPrompt(HttpContext ctx, DatabaseService db, MemoryService memoryService, SkillService skillService)
     {
         var sessionId = ctx.Request.RouteValues["sessionId"]?.ToString();
         if (string.IsNullOrEmpty(sessionId))
@@ -125,7 +125,8 @@ public static class SessionEndpoint
         var markedMessages = await db.GetMarkedMessages(sessionId);
         var agentMemoryDir = memoryService.GetAgentMemoryDir(agent.AgentId);
         var dataDir = memoryService.DataDir;
-        var systemPrompt = SystemPromptBuilder.Build(agent, session, markedMessages, memoryService, agentMemoryDir, dataDir);
+        var agentSkills = await db.GetAgentSkills(agent.AgentId);
+        var systemPrompt = SystemPromptBuilder.Build(agent, session, markedMessages, memoryService, agentMemoryDir, dataDir, agentSkills, skillService);
 
         ctx.Response.ContentType = "text/plain; charset=utf-8";
         await ctx.Response.WriteAsync(systemPrompt);

Endpoints/SkillEndpoint.cs

@@ -0,0 +1,82 @@
+using System.Linq;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Gott.Services;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+
+namespace Gott.Endpoints;
+
+public static class SkillEndpoint
+{
+    public static void MapSkillEndpoints(this IEndpointRouteBuilder app)
+    {
+        // Skills (Dateisystem-basiert)
+        app.MapGet("/api/skills", HandleListSkills);
+
+        // Agent ↔ Skill Zuordnung
+        app.MapGet("/api/agents/{agentId}/skills", HandleGetAgentSkills);
+        app.MapPut("/api/agents/{agentId}/skills", HandleSetAgentSkills);
+        app.MapPost("/api/agents/{agentId}/skills/{slug}", HandleAddAgentSkill);
+        app.MapDelete("/api/agents/{agentId}/skills/{slug}", HandleRemoveAgentSkill);
+    }
+
+    private static async Task HandleListSkills(HttpContext ctx, SkillService skillService)
+    {
+        var skills = skillService.GetAllSkills();
+        await ctx.Response.WriteAsJsonAsync(skills);
+    }
+
+    private static async Task HandleGetAgentSkills(HttpContext ctx, DatabaseService db, SkillService skillService)
+    {
+        var agentId = ctx.Request.RouteValues["agentId"]?.ToString();
+        if (string.IsNullOrEmpty(agentId)) { ctx.Response.StatusCode = 400; return; }
+
+        var slugs = await db.GetAgentSkills(agentId);
+        var allSkills = skillService.GetAllSkills();
+
+        // Nur Skills zurückgeben die auch wirklich existieren
+        var result = allSkills
+            .Where(s => slugs.Contains(s.Slug))
+            .ToList();
+
+        await ctx.Response.WriteAsJsonAsync(result);
+    }
+
+    private static async Task HandleSetAgentSkills(HttpContext ctx, DatabaseService db)
+    {
+        var agentId = ctx.Request.RouteValues["agentId"]?.ToString();
+        if (string.IsNullOrEmpty(agentId)) { ctx.Response.StatusCode = 400; return; }
+
+        var body = await JsonSerializer.DeserializeAsync<JsonElement>(ctx.Request.Body);
+        var slugs = body.TryGetProperty("skills", out var arr)
+            ? arr.EnumerateArray().Select(e => e.GetString()).Where(s => !string.IsNullOrEmpty(s)).ToList()
+            : new System.Collections.Generic.List<string>();
+
+        await db.SetAgentSkills(agentId, slugs);
+
+        var updated = await db.GetAgentSkills(agentId);
+        await ctx.Response.WriteAsJsonAsync(updated);
+    }
+
+    private static async Task HandleAddAgentSkill(HttpContext ctx, DatabaseService db)
+    {
+        var agentId = ctx.Request.RouteValues["agentId"]?.ToString();
+        var slug = ctx.Request.RouteValues["slug"]?.ToString();
+        if (string.IsNullOrEmpty(agentId) || string.IsNullOrEmpty(slug)) { ctx.Response.StatusCode = 400; return; }
+
+        await db.AddAgentSkill(agentId, slug);
+        ctx.Response.StatusCode = 204;
+    }
+
+    private static async Task HandleRemoveAgentSkill(HttpContext ctx, DatabaseService db)
+    {
+        var agentId = ctx.Request.RouteValues["agentId"]?.ToString();
+        var slug = ctx.Request.RouteValues["slug"]?.ToString();
+        if (string.IsNullOrEmpty(agentId) || string.IsNullOrEmpty(slug)) { ctx.Response.StatusCode = 400; return; }
+
+        await db.RemoveAgentSkill(agentId, slug);
+        ctx.Response.StatusCode = 204;
+    }
+}