Sandbox-Test: die Prozessgrenze zaehlt nur die Sandbox (#654)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/ClawdDotNet.Core.Tests/Sandbox/SandboxEscapeTests.cs

@@ -195,6 +195,17 @@ public sealed class SandboxEscapeTests : IDisposable
         (result.StandardError + result.StandardOutput).ShouldMatch("(?i)(fork|resource temporarily unavailable|cannot)");
     }
 
+    [SandboxFact]
+    public async Task The_limit_counts_the_sandbox_not_the_instances_threads()
+    {
+        // The instance itself runs hundreds of threads under the same user. Were those counted,
+        // the first fork would fail; five of ten must go.
+        var result = await Sh("i=0; while [ $i -lt 5 ]; do sleep 1 & i=$((i+1)); done; wait; echo started $i",
+            new SandboxLimits { Timeout = TimeSpan.FromSeconds(20), MaxProcesses = 10 });
+
+        result.StandardOutput.ShouldContain("started 5", customMessage: result.StandardError);
+    }
+
     [SandboxFact]
     public async Task The_programs_exit_code_comes_back()
         => (await Sh("exit 3")).ExitCode.ShouldBe(3);