fix(openviking): route viking_read to correct endpoint for file URIs

viking_read was calling /content/abstract and /content/overview for ALL
URIs, but these endpoints only accept directory URIs — file URIs cause
a 500 INTERNAL error.

Fix: call fs/stat first to determine URI type (isDir), then route:
- directory URIs  → /content/abstract | /content/overview | /content/read
- file URIs      → /content/read (handles both types, unlike abstract/overview)

Fixes #12755

plugins/memory/openviking/__init__.py

@@ -576,13 +576,27 @@ class OpenVikingMemoryProvider(MemoryProvider):
             return tool_error("uri is required")
 
         level = args.get("level", "overview")
-        # Map our level names to OpenViking GET endpoints
-        if level == "abstract":
-            resp = self._client.get("/api/v1/content/abstract", params={"uri": uri})
-        elif level == "full":
+
+        # Determine URI type so we route to the correct endpoint.
+        # abstract/overview are directory-only; files must use /content/download.
+        try:
+            stat_resp = self._client.get("/api/v1/fs/stat", params={"uri": uri})
+            is_dir = stat_resp.get("result", {}).get("isDir", False)
+        except Exception:
+            is_dir = False
+
+        if is_dir:
+            # Directory — route by level as before
+            if level == "abstract":
+                resp = self._client.get("/api/v1/content/abstract", params={"uri": uri})
+            elif level == "full":
+                resp = self._client.get("/api/v1/content/read", params={"uri": uri})
+            else:  # overview
+                resp = self._client.get("/api/v1/content/overview", params={"uri": uri})
+        else:
+            # File — abstract/overview endpoints don't support files;
+            # use /content/read which handles both types.
             resp = self._client.get("/api/v1/content/read", params={"uri": uri})
-        else:  # overview
-            resp = self._client.get("/api/v1/content/overview", params={"uri": uri})
 
         result = resp.get("result", "")
         # result is a plain string from the content endpoints