add files

.codex/skills/formula-quality/SKILL.md

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+---
+name: formula-quality
+description: Plan and review formula extraction quality for PDFtoMD. Use when Codex needs Nougat handoff rules, inline/block formula classification, LaTeX delimiter checks, equation numbering, reference anchors, or Marker fallback behavior.
+---
+
+# Formula Quality
+
+## Workflow
+
+1. Read `AGENTS.md`, `docs/CONVERSION_POLICY.md`, `docs/TOOLCHAIN.md`, and `docs/ADR.md`.
+2. Identify formula candidates from Marker equation blocks or mathematical text patterns.
+3. Classify formulas as inline or block based on layout context.
+4. Validate:
+   - `$ ... $` and `$$ ... $$` balance
+   - `\begin{...}` / `\end{...}` pairs
+   - formula numbering
+   - body references such as `Eq. (3)` or Korean equation references
+5. Use Marker source text as fallback when Nougat fails.
+
+## Guardrails
+
+- Do not pass whole documents through Nougat as the primary parser.
+- Do not discard formula text on parse failure.
+- Do not rewrite references as links unless the target confidence is sufficient.

.codex/skills/formula-quality/agents/openai.yaml

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+interface:
+  display_name: "Formula Quality"
+  short_description: "Validate equations and LaTeX output"
+  default_prompt: "Use $formula-quality to design formula parsing tests and fallback behavior."