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phases/4-semantic-enrichment/step0.md

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+# Step 0: reading-order-checks
+
+## Read First
+- /AGENTS.md
+- /PLAN.md
+- /PROGRESS.md
+- /docs/HARNESS.md
+- /docs/IMPLEMENTATION_PLAN.md
+- /docs/ARCHITECTURE.md
+- /docs/CONVERSION_POLICY.md
+- /phases/2-marker-adapter/step2.md
+
+## Task
+Create reading-order verification helpers over normalized blocks.
+
+Use page numbers and bounding boxes to detect obvious ordering anomalies in multi-column or inserted-text layouts.
+
+## Sprint Contract
+- Done means: reading-order checks produce diagnostics that later enrichment and evaluator steps can use.
+- Hard thresholds: checks are deterministic; tests include a multi-column-like fixture; helpers do not reorder content silently.
+- Files owned: `src/pdftomd/enrichment.py`, tests, `PROGRESS.md`, `phases/4-semantic-enrichment/index.json`.
+- Dependencies: Phase 2 normalized block model.
+
+## Acceptance Criteria
+```powershell
+python scripts\validate_workspace.py
+.\venv\python.exe -m pytest tests
+```
+
+## Verification
+1. Run the acceptance commands.
+2. Confirm diagnostics are actionable and tied to page/block ids.
+3. Update `PROGRESS.md` and this phase index.
+
+## Do Not
+- Do not override Marker ordering without tests.
+- Do not render Markdown.
+- Do not call Marker or Nougat.