fix(exec): clean up failed job assignment

tests/tools/test_exec_platform.py

@@ -8,7 +8,7 @@ platform-specific binaries (all subprocess calls are mocked).
 import asyncio
 import shutil
 import sys
-from unittest.mock import AsyncMock, patch
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
@@ -27,9 +27,6 @@ class _FakeWindowsJob:
     def assign_and_resume(self, pid: int) -> None:
         pass
 
-    def close(self) -> None:
-        pass
-
     def release(self) -> None:
         pass
 
@@ -149,6 +146,32 @@ class TestSpawnUnix:
 
 class TestSpawnWindows:
 
+    @pytest.mark.asyncio
+    async def test_job_assignment_failure_kills_suspended_process(self):
+        env = {"PATH": ""}
+        process = AsyncMock()
+        process.pid = 123
+        process.returncode = None
+        process.kill = MagicMock()
+        process.wait.return_value = -9
+        job = MagicMock(spec=_FakeWindowsJob)
+        job.creation_flags = 0x4
+        job.assign_and_resume.side_effect = OSError("OpenProcess failed")
+
+        with (
+            patch("nanobot.agent.tools.shell._IS_WINDOWS", True),
+            patch("nanobot.agent.tools.shell.sys.platform", "win32"),
+            patch("asyncio.create_subprocess_exec", new_callable=AsyncMock) as mock_exec,
+            patch.object(ExecTool, "_create_windows_job", return_value=job),
+            pytest.raises(OSError, match="OpenProcess failed"),
+        ):
+            mock_exec.return_value = process
+            await ExecTool._spawn("echo hi", r"C:\work", env, process_tree=True)
+
+        job.terminate.assert_called_once_with()
+        process.kill.assert_called_once_with()
+        process.wait.assert_awaited_once_with()
+
     @pytest.mark.asyncio
     async def test_single_line_uses_powershell(self):
         """Single-line commands on Windows now route through PowerShell."""