docs: RFC Ollama one-click local RAG

[MarcoPorcellato]

Context

README roadmap lists "Ollama Integration: One-click local RAG setup" with no linked design issue. This RFC captures scope before implementation.

Objectives

• Add docs/rfc/OLLAMA_RAG.md (or section in COOKBOOK) describing:
  • Target user story (local vault → embeddings → Ollama chat)
  • Dependencies ([ai] extra, optional Ollama binary)
  • Proposed CLI or script entry point (e.g. matryca-parse export + sample pipeline)
  • Non-goals (no cloud, no telemetry)
• Link RFC from README roadmap item
• Break implementation into follow-up issues

Files

• New: docs/rfc/OLLAMA_RAG.md
• README.md

Getting started

1. Review SynapseAdapter and existing export --format langchain flow
2. Research Ollama embedding/chat APIs (document links)

Out of scope

• Production Ollama integration code in this issue

Definition of Done

• RFC merged; follow-up issues filed for implementation slices