modify tolerance policy

docs/linear-static-mitc4-shell/reference-model.md

@@ -8,6 +8,7 @@
 - status: `approved-for-implementation-planning`
 - owner_agent: `reference-model-agent`
 - date: `2026-08-13`
+- comparison_revalidated_on: `2026-08-18`
 - artifact_policy: `read-only-existing-files`
 - authoritative_fesa_output: `results.h5`
 
@@ -80,26 +81,31 @@ zero-clamped and mismatched rows are not omitted, averaged, or synthesized.
 
 ## 5. Tolerance and decision rule
 
-For every matched row:
+Matched `U1/U2/U3` rows form one blocking translation family and matched
+`UR1/UR2/UR3` rows form one warning-only rotation family. For each family:
 
 ```text
-tolerance = 1.0e-5
-absolute_error_i = abs(fesa_value_i - abaqus_value_i)
+S = max(abs(abaqus_value_i))
+absolute_error_i = abs(fesa_value_i-abaqus_value_i)
+near_zero_band = 0.01*S
+
+near-zero row: absolute_error_i <= near_zero_band
+other row: absolute_error_i/abs(abaqus_value_i) <= 0.05
+relative_rms = sqrt(mean(absolute_error_i^2))/S <= 0.01
 ```
 
-The fixed `1.0e-5` value is expressed in the model's user-consistent length unit for
-`U1/U2/U3` and is dimensionless for `UR1/UR2/UR3`. Neither a component reference scale
-nor a row-specific denominator changes the value. Reference scale may be reported as
-non-decision diagnostic information. The separate B33 mixed tolerance is unchanged.
+The scale uses read-only Abaqus values only. No independent absolute-error gate, zero clamp or
+row omission is permitted. A zero-scale family passes only when all FESA values are exactly zero;
+otherwise it reports `zero-reference-scale-nonzero-error` without NaN/Inf. The U family controls
+the verdict and the UR family uses the same numeric rule for deterministic warning-only evidence.
 
-- Every matched `U1/U2/U3` row must satisfy `absolute_error_i <= tolerance`.
-  Any U exceedance fails that case and the feature reference comparison.
-- `UR1/UR2/UR3` uses the same fixed value. Every exceedance produces a deterministic
-  warning containing the case, source row, component, error, and tolerance, but does
-  not change pass/fail.
+- Every matched `U1/U2/U3` row and the translation family RMS must satisfy the common
+  row/RMS rule. Any U row or family-RMS exceedance fails the feature reference comparison.
+- `UR1/UR2/UR3` uses the same family-scale row/RMS rule. Every row or family-RMS
+  exceedance produces deterministic warning evidence but does not change pass/fail.
 
-The comparison report records every U/UR row decision, maximum absolute error,
-fixed-tolerance-normalized error, RMS error, vector-norm error, worst source
+The comparison report records every U/UR row decision, family scale, near-zero branch,
+maximum absolute error, row relative error, scale-relative RMS, worst source
 row/component, and every UR warning.
 
 ## 6. Coverage and handoff