updating and refining plugin system refactor

cmdlet/_shared.py

@@ -190,10 +190,18 @@ class SharedArgs:
         name="store",
         type="enum",
         choices=[],  # Dynamically populated via get_store_choices()
-        description="Selects store",
+        description="Selects a storage backend",
         query_key="store",
     )
 
+    INSTANCE = CmdletArg(
+        name="instance",
+        type="string",
+        description="Selects a plugin instance",
+        query_key="instance",
+        query_aliases=["store"],
+    )
+
     URL = CmdletArg(
         name="url",
         type="string",
@@ -1410,7 +1418,7 @@ def fetch_hydrus_metadata(
     Eliminates repeated boilerplate: client initialization, error handling, metadata extraction.
 
     Args:
-            config: Configuration object used to resolve the Hydrus provider/store
+            config: Configuration object used to resolve the Hydrus plugin/store
             hash_hex: File hash to fetch metadata for
             store_name: Optional Hydrus store name. When provided, do not fall back to a global/default Hydrus client.
             hydrus_client: Optional explicit Hydrus client. When provided, takes precedence.