Add agentic AI addons

[punkwalker]

Parent: #584
Priority: Medium

Add addon registry entries and charts for agentic AI workloads:

• Amazon Bedrock Agent runtime integration
• LangChain/LangGraph operator
• Vector database (pgvector, Milvus, or Weaviate)
• Model serving infrastructure (vLLM, TGI)
• Agent orchestration (CrewAI, AutoGen)
• Evaluation and observability (LangSmith, Phoenix)

Define as a new registry file ai.yaml or extend ml.yaml.