Agenten-Kostendeckel: LoopGuard + PermissionGate aus ClawdDotNet uebernommen

- Neu PolyTrader.Core/Agents: AgentBudget (Steps/Tokens/Timeout), LoopGuard
  (thread-safe, AgentBudgetExceededException mit Kind), PermissionGate
  (Tool-Allow-List, null = alle erlaubt). Aus ClawdDotNet portiert, NICHT als
  Abhaengigkeit (.NET 10 vs 8).
- SupervisorAgent nutzt LoopGuard (Default-Steps = MaxIterations=8, rueckwaerts-
  kompatibel) + PermissionGate (Allow-List = angebotene Tools; nicht freigegebene
  Calls liefern Fehlertext statt Ausfuehrung). SupervisorProfile.Budget ueber-
  schreibt den Deckel. Abbruch graceful mit Grund (Steps/Tokens/Zeit).
- Tests: AgentGuardTests (LoopGuard/PermissionGate) + Token-Abbruch am Agenten.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/PolyTrader.Tests/AgentGuardTests.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Threading;
+using PolyTrader.Core.Agents;
+using Xunit;
+
+namespace PolyTrader.Tests
+{
+    /// <summary>
+    /// Sicherheitsnetz für die aus ClawdDotNet übernommenen Agenten-Bausteine: LoopGuard (Kostendeckel
+    /// Schritte/Tokens/Zeit) und PermissionGate (Tool-Allow-List).
+    /// </summary>
+    public class AgentGuardTests
+    {
+        // ----- LoopGuard -----
+
+        [Fact]
+        public void LoopGuard_throws_when_step_limit_exceeded()
+        {
+            var guard = new LoopGuard(new AgentBudget { MaxSteps = 2, MaxTokens = 1_000_000, Timeout = TimeSpan.FromMinutes(5) });
+
+            guard.RecordStep();   // 1
+            guard.RecordStep();   // 2
+            var ex = Assert.Throws<AgentBudgetExceededException>(() => guard.RecordStep());   // 3 -> Abbruch
+            Assert.Equal(AgentBudgetKind.Steps, ex.Kind);
+        }
+
+        [Fact]
+        public void LoopGuard_throws_when_token_budget_exceeded()
+        {
+            var guard = new LoopGuard(new AgentBudget { MaxSteps = 100, MaxTokens = 100, Timeout = TimeSpan.FromMinutes(5) });
+
+            guard.RecordTokens(60);
+            var ex = Assert.Throws<AgentBudgetExceededException>(() => guard.RecordTokens(60));   // 120 > 100
+            Assert.Equal(AgentBudgetKind.Tokens, ex.Kind);
+            Assert.Equal(120, guard.Tokens);
+        }
+
+        [Fact]
+        public void LoopGuard_ignores_non_positive_token_counts()
+        {
+            var guard = new LoopGuard(new AgentBudget { MaxTokens = 10 });
+            guard.RecordTokens(0);
+            guard.RecordTokens(-5);
+            Assert.Equal(0, guard.Tokens);
+        }
+
+        [Fact]
+        public void LoopGuard_throws_when_time_budget_exceeded()
+        {
+            var guard = new LoopGuard(new AgentBudget { MaxSteps = 100, MaxTokens = 1_000_000, Timeout = TimeSpan.FromMilliseconds(10) });
+
+            Thread.Sleep(40);
+            var ex = Assert.Throws<AgentBudgetExceededException>(() => guard.ThrowIfExpired());
+            Assert.Equal(AgentBudgetKind.Time, ex.Kind);
+        }
+
+        // ----- PermissionGate -----
+
+        [Fact]
+        public void PermissionGate_allows_listed_tool_case_insensitive()
+        {
+            var gate = new PermissionGate();
+            var allowed = new[] { "read_logs", "query_trades" };
+
+            Assert.True(gate.IsAllowed("READ_LOGS", allowed));
+            Assert.False(gate.IsAllowed("place_order", allowed));
+        }
+
+        [Fact]
+        public void PermissionGate_null_allowlist_permits_everything()
+        {
+            var gate = new PermissionGate();
+            Assert.True(gate.IsAllowed("anything", null));
+        }
+
+        [Fact]
+        public void PermissionGate_enforce_throws_for_denied_tool()
+        {
+            var gate = new PermissionGate();
+            Assert.Throws<ToolAccessDeniedException>(() => gate.Enforce("place_order", new[] { "read_logs" }));
+        }
+    }
+}

tests/PolyTrader.Tests/SupervisorAgentTests.cs

@@ -101,6 +101,25 @@ namespace PolyTrader.Tests
             Assert.Equal(SupervisorAgent.MaxIterations, result.ToolInvocations.Count);
         }
 
+        [Fact]
+        public async Task Agent_aborts_when_token_budget_exceeded()
+        {
+            // Erste Antwort verbraucht bereits mehr Tokens als das Budget -> Abbruch VOR Tool-Ausführung.
+            var chat = new ScriptedChatClient(
+                new ChatResponse { PromptTokens = 80, CompletionTokens = 80,
+                    ToolCalls = { new ToolCall("c1", "echo", "{}") } });
+            var agent = new SupervisorAgent(chat, RegistryWithEcho());
+            var profile = new SupervisorProfile("Knapp", "", null)
+            {
+                Budget = new PolyTrader.Core.Agents.AgentBudget { MaxTokens = 100, MaxSteps = 100 }
+            };
+
+            var result = await agent.AskAsync("x", profile: profile);
+
+            Assert.Contains("Token-Budget erschöpft", result.Answer);
+            Assert.Empty(result.ToolInvocations);
+        }
+
         // ----- OpenRouter-Serialisierung (pur) -----
 
         [Fact]