feat: integrate RAG rag_jrxml submodule and fix Anthropic API key

Add rag submodule for semantic JRXML chunk retrieval, refactor
retrieve node to use RAGSearcher, and fix missing api_key in
Anthropic SDK client initialization.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitignore

@@ -12,6 +12,14 @@ dist/
 db/chroma/
 sessions/
 
+# RAG 管线中间产物 (rag 子模块内)
+rag/jrxml_chunker_output/
+rag/embeddings/
+rag/models/
+rag/__pycache__/
+rag/chroma_db/
+rag/jrxml_source_chunks/
+
 # IDE
 .idea/
 .vscode/