Skip integer overflow tests on CRAN

Add skip_on_cran() to two tests in tests/testthat/test-cpp_math_primitives.R (cpp_grouped_sums and cpp_multi_grouped_sums) so they are skipped during CRAN checks. These tests already skip on macOS and cover integer overflow/matrix-dimension edge cases that can cause false failures on CRAN.

Author: zankrut20

tests/testthat/test-cpp_math_primitives.R

@@ -625,6 +625,7 @@ test_that("cpp_mean_squares handles larger matrices", {
 # ==============================================================================
 
 test_that("cpp_grouped_sums triggers invalid matrix dimensions on integer overflow", {
+  skip_on_cran()
   skip_on_os("mac")
   data_mat <- matrix(1.0, nrow = 1, ncol = 1)
   # R NA_integer_ is -2147483648, which underflows/overflows when processed in C++.
@@ -639,6 +640,7 @@ test_that("cpp_grouped_sums triggers invalid matrix dimensions on integer overfl
 })
 
 test_that("cpp_multi_grouped_sums triggers invalid number of groups on integer overflow", {
+  skip_on_cran()
   skip_on_os("mac")
   data_mat <- matrix(1.0, nrow = 1, ncol = 1)
   group_indices <- list(c(NA_integer_))