fix: resolve per-torrent qb save paths

tests/test_deployment_preflight.py

@@ -50,6 +50,26 @@ class DeploymentPreflightTests(unittest.TestCase):
             "/data/qb/.archive-control-routes",
         )
 
+    def test_qb_override_must_map_to_the_same_host_path(self):
+        client = {"Mounts": [
+            {"Type": "bind", "Source": "/srv/fast", "Destination": "/data/fast"},
+        ]}
+        qbittorrent = {"Mounts": [
+            {"Type": "bind", "Source": "/srv/fast", "Destination": "/downloads/fast"},
+        ]}
+        preflight.require_qb_override_mappings(
+            client, qbittorrent,
+            {"local_path_overrides": {"/downloads/fast": "/data/fast"}},
+        )
+        with self.assertRaisesRegex(preflight.CheckFailure, "host paths differ"):
+            preflight.require_qb_override_mappings(
+                client,
+                {"Mounts": [{
+                    "Type": "bind", "Source": "/other", "Destination": "/downloads/fast",
+                }]},
+                {"local_path_overrides": {"/downloads/fast": "/data/fast"}},
+            )
+
     def test_runs_hardlink_probe_with_qb_and_route_roots(self):
         completed = __import__("subprocess").CompletedProcess(
             args=[], returncode=0, stdout="hard-link staging probe passed\n", stderr=""