docs: use S4-only MITC4 reference gate

docs/research/linear-static-mitc4-shell-research.md

@@ -6,10 +6,10 @@
 - source_requirement: `docs/requirements/linear-static-mitc4-shell.md`
 - status: `approved`
 - owner_agent: `research-agent`
-- date: `2026-08-12`
+- date: `2026-08-13`
 - product_scope: small-displacement, small-rotation, single-step linear static analysis
 - evidence_route: local papers in `docs/reference-papers/MITC4/`, the configured FEM wiki, original peer-reviewed papers, and official Abaqus documentation
-- reference_inventory_state: existing read-only S4 case at `reference/shell/` and S4R case at `reference/shellR/`; exact comparison paths are fixed by the approved requirements
+- reference_inventory_state: the sole acceptance comparison is the existing read-only full-integration S4 case at `reference/shell/`; S4R source support is verified without consuming an Abaqus reference artifact
 - source_policy: each external claim below is assigned a reliability tier; FESA decisions are labeled `Project contract`, and derived recommendations are labeled `Inference` or `Research recommendation`
 
 This brief supplies evidence to the Formulation, Numerical Review, I/O Definition, and
@@ -25,7 +25,7 @@ formulation-equivalent to Abaqus S4 or S4R.
 4. What evidence and dimensional restriction support the approved fixed drilling stabilization without turning it into a physical strain or load channel?
 5. What evidence supports connectivity-derived thickness directions, nodal-normal smoothing, local tangent frames, and geometry rejection?
 6. What may and may not be inferred when Abaqus S4 and S4R input types are both mapped to one FESA MITC4 formulation?
-7. Which element-level checks and the declared S4/S4R source-solver cases fit the approved implementation scope?
+7. Which element-level checks and the declared full-integration S4 source-solver case fit the approved implementation scope while retaining non-reference S4R mapping coverage?
 
 ## Source Reliability Tiers
 
@@ -146,7 +146,7 @@ problems must not be mixed.
 - **Locking and convergence:** thin/thick cantilevers, pinched cylinder, LE3, and Scordelis–Lo remain useful future studies. They are not additional completion gates for the approved two-case implementation scope.
 - **Geometry verification:** tests must evaluate every formulation-required Gauss and tying location, not only the element center. Director smoothing and Jacobian quality are separate checks; a smooth director cannot rescue a self-intersecting or inverted mapping.
 - **Drilling verification:** verify the fixed formula, dimensional family, symmetry, positivity, four-mode regularization, and absence from physical `E/N/M/Q/stress` recovery. Sensitivity and artificial-energy evidence are excluded.
-- **Reference comparison:** the declared S4 and S4R cases test source mapping and global displacement. They cannot prove formulation identity. Missing, extra, duplicate, nonfinite, or source-node/component-mismatched required rows fail before P1's mixed displacement tolerance is evaluated.
+- **Reference comparison:** the declared S4 case tests full-integration source mapping and global displacement. It cannot prove formulation identity. Missing, extra, duplicate, nonfinite, or source-node/component-mismatched required rows fail before P1's mixed displacement tolerance is evaluated. S4R source support is established separately by FESA mapping/kernel/metadata tests.
 - **Physics sanity:** force and global moment balance, symmetry, displacement direction, reaction sign, positive physical energy, free residual, and consistency of recovered resultants remain mandatory even when all reference displacement rows pass.
 - **Validation boundary:** the identified sources provide analytical, benchmark, and source-solver verification. No experimental dataset was established for the approved homogeneous linear-static feature; physical validation remains N/A unless separately added.
 
@@ -181,7 +181,7 @@ problems must not be mixed.
 1. **Drilling:** P1 fixes the positive physical-rotational-diagonal scale and `10^-3` factor. Alternative-family comparison, coefficient sweep, conditioning plateau and artificial-energy threshold are not required.
 2. **Director/geometry:** `NR-O03` and `NR-O04` are removed. The absence of a calibrated smooth angle or distortion/warp cutoff is not missing evidence.
 3. **Reference tolerance:** P1 reuses the B33 formula `1e-9 + 1e-6*reference_scale_c`; U exceedance fails and UR exceedance only warns.
-4. **Reference cases:** the existing `reference/shell/` S4 and `reference/shellR/` S4R input/displacement pairs are the complete required inventory. Administrative bundle metadata and an expanded portfolio are not gates.
+4. **Reference case:** the existing `reference/shell/` S4 input/displacement pair is the complete required acceptance inventory because FESA-MITC4 uses full integration. `reference/shellR/` is not consumed by acceptance comparison. Administrative bundle metadata and an expanded portfolio are not gates.
 
 No research-owned numerical decision remains blocking for Implementation Planning.
 
@@ -196,7 +196,7 @@ No research-owned numerical decision remains blocking for Implementation Plannin
 | `039-048` shell outputs | F-09–F-11/F-18 | physical shell output and bottom/mid/top stress locations; no drilling-specific dataset |
 | `049-057` element verification | F-28/F-29 and Candidate Benchmarks | required invariant/patch/fixed-drill checks; broader portfolio remains optional |
 | `058-064` U/UR tolerance | F-25–F-27 plus P1 | exact B33 mixed tolerance; U blocking and UR warning-only |
-| `065-072` reference artifacts | S11/S12 and current inventory state | exact existing S4/S4R paths, source-row/component mapping, and immutability |
+| `065-072` reference artifacts | S11/S12 and current inventory state | exact existing S4 paths, source-row/component mapping, S4R non-consumption, and immutability |
 
 ## Downstream Handoff