docs(readme,strings): YAML seed-only semantics documented — interactive flow, duplicate guards, no implicit entry changes on block removal (t30 U1)

custom_components/nvidia_shield/strings.json

@@ -62,7 +62,12 @@
       "already_configured": "This Shield entity is already configured.",
       "reauth_successful": "Re-paired successfully.",
       "reauth_entry_missing": "This entry no longer exists.",
-      "zeroconf_no_host": "The discovery event carried no usable address."
+      "zeroconf_no_host": "The discovery event carried no usable address.",
+      "yaml_seed_only": {},
+      "yaml_seed": {
+        "title": "YAML succeeded earlier",
+        "message": "The configuration.yaml nvidia_shield block is seed-only: it starts the standard interactive flow. Removing the YAML block creates or deletes nothing."
+      }
     }
   },
   "options": {