fix(skills): remove phantom resource references and fix CoC links (#447)

Remove references to non-existent resource files (references/, assets/,
scripts/, examples/) from 115 skill SKILL.md files. These sections
pointed to directories and files that were never created, causing
confusion when users install skills.

Also fix broken Code of Conduct links in issue templates to use
absolute GitHub URLs instead of relative paths that 404.

plugins/llm-application-dev/skills/rag-implementation/SKILL.md

@@ -540,31 +540,3 @@ async def evaluate_rag_system(
 
     return {k: sum(v) / len(v) for k, v in metrics.items()}
 ```
-
-## Resources
-
-- [LangChain RAG Tutorial](https://python.langchain.com/docs/tutorials/rag/)
-- [LangGraph RAG Examples](https://langchain-ai.github.io/langgraph/tutorials/rag/)
-- [Pinecone Best Practices](https://docs.pinecone.io/guides/get-started/overview)
-- [Voyage AI Embeddings](https://docs.voyageai.com/)
-- [RAG Evaluation Guide](https://docs.ragas.io/)
-
-## Best Practices
-
-1. **Chunk Size**: Balance between context (larger) and specificity (smaller) - typically 500-1000 tokens
-2. **Overlap**: Use 10-20% overlap to preserve context at boundaries
-3. **Metadata**: Include source, page, timestamp for filtering and debugging
-4. **Hybrid Search**: Combine semantic and keyword search for best recall
-5. **Reranking**: Use cross-encoder reranking for precision-critical applications
-6. **Citations**: Always return source documents for transparency
-7. **Evaluation**: Continuously test retrieval quality and answer accuracy
-8. **Monitoring**: Track retrieval metrics and latency in production
-
-## Common Issues
-
-- **Poor Retrieval**: Check embedding quality, chunk size, query formulation
-- **Irrelevant Results**: Add metadata filtering, use hybrid search, rerank
-- **Missing Information**: Ensure documents are properly indexed, check chunking
-- **Slow Queries**: Optimize vector store, use caching, reduce k
-- **Hallucinations**: Improve grounding prompt, add verification step
-- **Context Too Long**: Use compression or parent document retriever