docs: redefine phase 1 rebaseline steps

phases/1-linear-static-mitc4-rebaseline/step8.md

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+# Sprint Contract: MITC4 Covariant Strain Tying
+
+## Objective
+Implement or rebuild the degenerated-continuum displacement interpolation, direct covariant strain rows, and MITC transverse shear tying interpolation.
+
+## Required Reading
+- /AGENTS.md
+- /docs/MITC4_FORMULATION.md
+- /docs/NUMERICAL_CONVENTIONS.md
+
+## Scope
+- Implement five-DOF local displacement interpolation.
+- Transform global rotations to local `alpha`, `beta`, and `gamma`.
+- Compute direct covariant strain rows in documented internal strain order.
+- Replace `eps_13` and `eps_23` with midside MITC tying interpolation.
+- Add finite-difference tests for strain rows.
+
+## Allowed Files
+- `include/`
+- `src/`
+- `tests/`
+- `PLAN.md`
+- `PROGRESS.md`
+
+## Explicit Non-Goals
+- Do not integrate stiffness.
+- Do not add material transform.
+- Do not compute MITC shear from Cartesian `gamma_xz` and `gamma_yz` first.
+
+## Tests To Write First
+- Local rotation transform tests for `alpha`, `beta`, `gamma`.
+- Displacement interpolation tests at midsurface and through-thickness points.
+- Direct covariant strain finite-difference tests.
+- Tying-row tests at `A`, `B`, `C`, and `D`.
+- Gauss-point MITC shear interpolation tests proving rows come from tying rows.
+
+## Reference Artifacts
+- None.
+
+## Acceptance Commands
+```bash
+python scripts/validate_workspace.py
+```
+
+## Evaluator Checklist
+- Strain vector ordering is documented or explicitly permuted.
+- `gamma` does not contribute to physical continuum strain.
+- FESA sign convention for `A/C/B/D` is tested.
+
+## Handoff Requirements
+- Record strain/tying readiness in `PROGRESS.md`.
+
+## Do Not
+- Do not reintroduce direct Gauss-point transverse shear for MITC rows.