feat: complete first MITC4 FEAST eigen implementation validation

tests/reference/eigen_reference_comparison_test.cpp

@@ -5,9 +5,12 @@
 
 #include <atomic>
 #include <chrono>
+#include <cmath>
 #include <filesystem>
 #include <fstream>
+#include <limits>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "fesa/io/abaqus/input_reader.h"
@@ -117,7 +120,32 @@ TEST(EigenReferenceComparison,
   auto reference_case = fesa::test::EigenReferenceCase{"x", inp, txt, h5};
   auto ok = fesa::test::EigenReferenceComparison::Compare(reference_case);
   ASSERT_TRUE(ok.HasValue());
+  EXPECT_EQ(ok.Value().policy_id, "mitc4-eigen-first-implementation");
+  EXPECT_DOUBLE_EQ(ok.Value().relative_rms_tolerance, 0.05);
   EXPECT_EQ(ok.Value().families.size(), 2U);
+  // Only synthetic FESA output is changed; each TXT mode remains an independent
+  // scalar family, including at both inclusive five-percent boundaries.
+  for (const auto& sample :
+       std::vector<std::pair<double, bool>>{
+           {103.0, true}, {105.0, true}, {95.0, true},
+           {std::nextafter(105.0, std::numeric_limits<double>::infinity()), false},
+           {std::nextafter(95.0, 0.0), false}}) {
+    SCOPED_TRACE(sample.first);
+    f = H5Fopen(h5.string().c_str(), H5F_ACC_RDWR, H5P_DEFAULT);
+    ds = H5Dopen2(f, "/steps/Step-1/eigen/modes", H5P_DEFAULT);
+    t = H5Dget_type(ds);
+    v[0].eigenvalue = sample.first;
+    ASSERT_GE(H5Dwrite(ds, t, H5S_ALL, H5S_ALL, H5P_DEFAULT, v), 0);
+    H5Tclose(t);
+    H5Dclose(ds);
+    H5Fclose(f);
+    const auto comparison =
+        fesa::test::EigenReferenceComparison::Compare(reference_case);
+    ASSERT_TRUE(comparison.HasValue());
+    EXPECT_EQ(comparison.Value().passed, sample.second);
+    EXPECT_EQ(comparison.Value().families[0].rms_passed, sample.second);
+    EXPECT_TRUE(comparison.Value().families[1].passed);
+  }
   struct TextMutation {
     std::string text;
     std::string expected_code;