docs: redefine phase 1 rebaseline steps

phases/1-linear-static-mitc4-rebaseline/step6.md

@@ -0,0 +1,57 @@
+# Sprint Contract: Results Comparator Foundation
+
+## Objective
+Rebuild or verify the minimum Phase 1 results model and Abaqus displacement CSV comparator before using stored reference regressions.
+
+## Required Reading
+- /AGENTS.md
+- /docs/RESULTS_SCHEMA.md
+- /docs/VERIFICATION_PLAN.md
+- /docs/NUMERICAL_CONVENTIONS.md
+
+## Scope
+- Store minimum result model data for nodes, elements, `U`, and `RF`.
+- Preserve step/frame/field structure even if HDF5 writing is deferred.
+- Load Abaqus `*_displacements.csv` by node id and component label.
+- Compare using absolute and relative tolerances.
+
+## Allowed Files
+- `include/`
+- `src/`
+- `tests/`
+- `docs/RESULTS_SCHEMA.md` only for clarifying schema text
+- `docs/VERIFICATION_PLAN.md` only for clarifying tolerance/reference text
+- `PLAN.md`
+- `PROGRESS.md`
+
+## Explicit Non-Goals
+- Do not make `S`, `E`, or `SF` mandatory.
+- Do not require Abaqus execution.
+- Do not rely on CSV row order.
+
+## Tests To Write First
+- `U` and `RF` field component labels and basis tests.
+- CSV required-header tests.
+- Duplicate/missing/non-numeric node row tests.
+- Node-id-based comparison tests with absolute and relative tolerance paths.
+- Result frame metadata tests for Phase 1 linear static frame 0.
+
+## Reference Artifacts
+- `references/quad_02_displacements.csv`
+- `references/quad_01_displacements.csv`
+
+## Acceptance Commands
+```bash
+python scripts/validate_workspace.py
+```
+
+## Evaluator Checklist
+- Result component order matches docs.
+- Comparator maps Abaqus columns to FESA `U` labels exactly.
+- `RF` exists as a result field even if Abaqus RF CSV is unavailable.
+
+## Handoff Requirements
+- Record comparator readiness and remaining RF artifact decision in `PROGRESS.md` and `PLAN.md`.
+
+## Do Not
+- Do not add undocumented CSV formats.