docs: require hardlink-safe route mount topology

docs/service-apis.md

@@ -89,9 +89,11 @@ left unchanged.
 
 Syncthing may serialize a folder path relative to its home as `~/...`. The
 client normalizes that notation beneath the configured API-visible sync root
-before applying the API-to-local root mapping. Deployments must mirror
-Syncthing's nested bind mounts into the client so the normalized API path and
-the client filesystem path refer to the same bytes.
+before applying the API-to-local root mapping. When that folder is nested
+below qB's content root, an exact `local_path_overrides` entry must map it
+through the qB bind mount. Do not mirror it as a second nested client bind
+mount: it denotes the same host bytes but a distinct mount namespace boundary,
+which prevents hardlink staging.
 
 Provisioning uses idempotent device and folder configuration updates. Each
 client receives its peer device ID and optional advertised addresses