chore: update model references to Claude 4.6 and GPT-5.2

- Claude Opus 4.5 → Opus 4.6, Claude Sonnet 4.5 → Sonnet 4.6 (Haiku stays 4.5)
- Update claude-sonnet-4-5 model IDs to claude-sonnet-4-6 in code examples
- Update SWE-bench stat from 80.9% to 80.8% for Opus 4.6
- Update GPT refs: GPT-5 → GPT-5.2, GPT-4o → gpt-5.2, GPT-4o-mini → GPT-5-mini
- Fix GPT-5.2-mini → GPT-5-mini (correct model name per OpenAI)
- Bump marketplace to v1.5.2 and affected plugin versions

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

@@ -85,7 +85,7 @@ class RAGState(TypedDict):
     answer: str
 
 # Initialize components
-llm = ChatAnthropic(model="claude-sonnet-4-5")
+llm = ChatAnthropic(model="claude-sonnet-4-6")
 embeddings = VoyageAIEmbeddings(model="voyage-3-large")
 vectorstore = PineconeVectorStore(index_name="docs", embedding=embeddings)
 retriever = vectorstore.as_retriever(search_kwargs={"k": 4})