fix: preserve task stop intent and guard remote execution boundaries

backend/tests/test_background_tasks.py

@@ -106,6 +106,30 @@ class TaskServiceTest(unittest.IsolatedAsyncioTestCase):
         await self.wait_status(second["id"], "cancelled")
         self.assertEqual(SimulatedExecutor.calls, 1)
 
+    async def test_restart_retries_pending_stop_instead_of_resuming_execution(self):
+        SimulatedExecutor.confirms_stop = False
+        task = await self.submit()
+        await self.wait_status(task["id"], "running")
+        await self.service.cancel(task["id"])
+        async with asyncio.timeout(2):
+            while self.service.runtime.executor.active_jobs:
+                await asyncio.sleep(.005)
+        await self.service.close()
+        SimulatedExecutor.confirms_stop = True
+        await self.service.start()
+        await self.wait_status(task["id"], "cancelled")
+        self.assertEqual(SimulatedExecutor.calls, 1)
+
+    async def test_unconfirmed_remote_stop_blocks_the_next_submission(self):
+        SimulatedExecutor.confirms_stop = False
+        first = await self.submit("call_first")
+        await self.wait_status(first["id"], "running")
+        second = await self.submit("call_second")
+        await self.service.cancel(first["id"])
+        await self.wait_status(second["id"], "failed")
+        self.assertEqual(SimulatedExecutor.calls, 1)
+        self.assertFalse((await self.service.get(second["id"])).remote_handle)
+
     async def test_restart_observes_existing_remote_handle(self):
         task = await self.submit()
         await self.wait_status(task["id"], "running")