add files

.codex/skills/conversion-architecture/SKILL.md

@@ -0,0 +1,23 @@
+---
+name: conversion-architecture
+description: Design PDFtoMD conversion architecture, parser boundaries, internal block models, chunk policy, renderer contracts, output structure, logging, and resume behavior. Use when planning or reviewing conversion engine design.
+---
+
+# Conversion Architecture
+
+## Workflow
+
+1. Read `AGENTS.md`, `PLAN.md`, `PROGRESS.md`, `docs/ARCHITECTURE.md`, `docs/CONVERSION_POLICY.md`, and `docs/ADR.md`.
+2. Keep responsibilities stable:
+   - Marker: layout, OCR, reading order, body, headings, tables, figures, captions
+   - Nougat: formula-only LaTeX parsing
+   - PyMuPDF: page pre-analysis, text-layer quality, page counts, chunk planning
+3. Define interfaces and invariants before implementation.
+4. Keep output deterministic and chunked under the documented output contract.
+5. Record architecture changes in `docs/ADR.md` when decisions change.
+
+## Guardrails
+
+- Do not place conversion logic in a future PyQt UI.
+- Do not add document sidecars unless explicitly requested.
+- Do not let chunking split a paragraph, table, figure, or formula without a fallback plan.