docs: clarify qB save path resolution

src/archive_clients/resources.py

@@ -19,6 +19,14 @@ class ResourceError(ValueError):
 
 @dataclass(frozen=True)
 class NormalizedResource:
+    """A normalized qB observation for protocol data and local file work.
+
+    ``save_path`` is qBittorrent's API-visible per-torrent content root.  It
+    is deliberately local-only: clients resolve it through their qB path
+    mapping immediately before filesystem work, and it is never serialized in
+    inventory, placements, or control protocol messages.
+    """
+
     summary: resource_pb2.ResourceSummary
     files: tuple[resource_pb2.TorrentFile, ...]
     metainfo: Metainfo