Bring-your-own-model for agentic extraction (OpenAI, Ollama)

[kiyeonjeon21]

Today agentic extraction is Claude Haiku 4.5 only. Open it up.

Proposed:

• CONTEXTIX_MODEL=openai:gpt-4o-mini or CONTEXTIX_MODEL=ollama:llama3.2
• Adapter pattern: new src/extract/models/openai.ts, ollama.ts
• Share the strict tool_use schema; each adapter translates

Why matters: offline use (ollama), cost control (cheaper alternatives), avoiding vendor lock-in.

Scope: medium. Per-adapter ~100 lines plus shared plumbing.