Fix CodeRabbit review: lowercase negative pattern, add missing docstring

- "DockerClient" → "dockerclient" in docker skill's negative list
  (mixed-case never matched against lowered input)
- Add docstring to main() to meet 80% coverage threshold

Author: AnExiledDev

.devcontainer/plugins/devs-marketplace/plugins/skill-engine/scripts/skill-suggester.py

@@ -188,7 +188,7 @@
         ],
         "terms": ["dockerfile", "compose.yaml", "BuildKit"],
         "negative": ["docker-py", "docker py", "docker sdk", "docker from python",
-                     "aiodocker", "DockerClient"],
+                     "aiodocker", "dockerclient"],
         "context_guards": [
             "docker", "container", "compose", "image", "dockerfile",
         ],
@@ -639,6 +639,7 @@ def match_skills(prompt: str) -> list[str]:
 
 
 def main() -> None:
+    """Read a hook event from stdin, score skills, and print suggestions to stdout."""
     raw = sys.stdin.read().strip()
     if not raw:
         return