Review fix on #351: comment rationale + repair a rebase-seam brace

Updates the set_symmetric no-op comment (the MinorMajor early-return
it cited is gone; the rank gate is the actual reason at rank 4) and
repairs a conflict-resolution artifact that glued a test's closing
brace into a trailing comment, leaving the test namespace open.

Signed-off-by: petlenz <peterlenz89.pl@gmail.com>

Author: petlenz

include/numsim_cas/tensor/identity_tensor.h

@@ -106,10 +106,9 @@ class identity_tensor final : public tensor_node_base_t<identity_tensor> {
       a.insert(positive_semidefinite{}); // PD ⇒ PSD, mirrors
                                          // assume_positive_definite()
       // PD ⇒ symmetric, via the same helper assume_positive_definite()
-      // uses. Mechanically a no-op today because space_for_rank above
-      // already wrote a qualifying space tag at both supported ranks
-      // (rank-2 Symmetric ⇒ ProjKind::Sym early-return; rank-4
-      // MinorMajor ⇒ holds_alternative early-return). The call exists
+      // uses. Mechanically a no-op today: rank-2 already carries
+      // Symmetric, and the helper's rank()!=2 gate skips rank 4 (whose
+      // tag is Major since #351). The call exists
       // so that any future drift in detail::set_symmetric_unless_more_specific
       // (e.g. it grows a sibling-field write that we'd otherwise miss)
       // tracks automatically. Pairs with the helper in tensor_assume.h.

tests/CoreBugFixTest.h

@@ -1786,7 +1786,8 @@ TEST(Rank4IdentityTag, InvOfNegatedIdentity) {
   auto r = ev.apply(inv(-I4));
   // (0,1,0,1) flattens to ((0*3+1)*3+0)*3+1 = 10
   EXPECT_NEAR(r->raw_data()[10], -1.0, 1e-12);
-  EXPECT_NEAR(r->raw_data()[0], -1.0, 1e-12); // (0,0,0,0)}
+  EXPECT_NEAR(r->raw_data()[0], -1.0, 1e-12); // (0,0,0,0)
+}
 
 } // namespace numsim::cas