[DOC] Add ecosystem integrations track (LangChain/LangGraph/LlamaIndex/Haystack)

[tazarov]

Why

A major gap is ecosystem integration guidance. Users need practical integration patterns across major frameworks.

Proposal

Add a dedicated ecosystem integrations track with deep examples and decision guidance.

Scope

• Cover practical Chroma integration patterns for:
  • LangChain / LangGraph
  • LlamaIndex
  • Haystack
• Provide framework selection guidance by use case (RAG app, agent workflow, evaluation-heavy pipeline).
• Include compatibility notes and version pin recommendations.

Deliverables

• Integrations overview page with links to deep walkthroughs.
• At least one runnable example per framework.
• Comparison table (capabilities, complexity, tradeoffs).

Acceptance Criteria

• Users can choose an integration path from the guide without external research.
• Each framework example is runnable and validated.
• The track links directly to deeper production-oriented cookbook recipes.