Add arbitrary fixed-effect contrasts

include/spectra_reml/batch_io.hpp

@@ -20,6 +20,8 @@ struct BatchInputPaths {
     std::filesystem::path tasks_tsv;
     std::filesystem::path extra_offsets_i64;
     std::filesystem::path extra_indices_i32;
+    std::filesystem::path contrast_matrix_f64;
+    std::filesystem::path contrast_metadata_tsv;
     std::filesystem::path output_directory;
 };
 
@@ -28,6 +30,7 @@ struct BatchDimensions {
     std::size_t base_covariate_count = 0;
     std::size_t phenotype_row_count = 0;
     std::size_t extra_covariate_row_count = 0;
+    std::size_t contrast_count = 0;
 };
 
 struct BatchOptions {

include/spectra_reml/types.hpp

@@ -164,6 +164,10 @@ struct RemlResult {
     std::vector<double> beta_covariance_packed_lower;
     FixedEffectInferenceResult fixed_effect_inference;
     FixedEffectTestResult extra_fixed_effect_joint_test;
+    // Named shared contrasts supplied by the batch interface, in manifest
+    // contrast order.  Every contrast acts on the common/base fixed effects;
+    // task-specific fixed-effect columns are assigned zero weight.
+    std::vector<FixedEffectTestResult> contrast_tests;
     std::string error;
 
     [[nodiscard]] bool has_estimates() const noexcept {