(bugfix) Reconcile failed dry-runs from rsync terminal logs

Classify rsync failures in run results so transport issues such as exit
255 and broken pipes show clearer diagnostic hints.

Teach the worker to reconcile running dry-runs when their log already
contains a terminal rsync error, and to fail stale dry-runs after their
timeout window. This prevents failed rsync processes from leaving runs
stuck in the running state indefinitely.

src/pobsync_backend/tests/test_run_scheduled_config_source.py

@@ -66,6 +66,30 @@ class RunScheduledConfigSourceTests(SimpleTestCase):
         self.assertFalse(result["ok"])
         self.assertEqual(result["rsync"]["exit_code"], 12)
         self.assertEqual(result["rsync"]["log_tail"], ["Permission denied (publickey).", "rsync error"])
+        self.assertEqual(result["failure"]["category"], "permissions")
+
+    def test_failed_dry_run_classifies_broken_pipe(self) -> None:
+        def fake_run_rsync(command, log_path, timeout_seconds, cancel_check=None):
+            log_path.parent.mkdir(parents=True, exist_ok=True)
+            log_path.write_text(
+                "rsync error: unexplained error (code 255) at rsync.c(716) [generator=3.4.1]\n"
+                "rsync: [generator] write error: Broken pipe (32)\n",
+                encoding="utf-8",
+            )
+            return RsyncResult(exit_code=255, command=command)
+
+        with patch("pobsync.commands.run_scheduled.run_rsync", side_effect=fake_run_rsync):
+            result = run_scheduled(
+                prefix=Path("/missing-prefix"),
+                host="web-01",
+                dry_run=True,
+                config_source=FakeConfigSource(),
+            )
+
+        self.assertFalse(result["ok"])
+        self.assertEqual(result["rsync"]["exit_code"], 255)
+        self.assertEqual(result["failure"]["category"], "transport")
+        self.assertIn("broken pipe", result["failure"]["hint"].lower())
 
     def test_dry_run_clears_previous_log_before_running(self) -> None:
         def fake_run_rsync(command, log_path, timeout_seconds, cancel_check=None):