Convert the PDF-embedded-image document-context item (TODO.md L3) into phase 137_pdf_image_context (Protocol B append, 5 tasks): per-page text extraction, the forward context path into the vision prompt + image_context, the idempotent per-sync backfill for existing image docs, the From-loc display line, and the dedicated E2E suite. TODO.md cleared (items now live in .agents/phases/). LLM-Generated: true