chore: vendor blender-mcp as a git submodule alongside godot-mcp

Both mcp/godot-mcp and mcp/blender-mcp were already cloned locally and
registered in .gitmodules/.mcp.json/CLAUDE.md, but neither submodule's
gitlink had actually been committed, so a fresh clone wouldn't pull
either down. Stages the two gitlinks so `git submodule update --init
--recursive` works as documented.

.mcp.json

@@ -6,6 +6,10 @@
       "env": {
         "GODOT_PATH": ""
       }
+    },
+    "blender": {
+      "command": "uv",
+      "args": ["run", "--project", "mcp/blender-mcp", "blender-mcp"]
     }
   }
 }