fix: use BB_ASSERT_EQ instead of BB_ASSERT for WNAF scalar sum check

BB_ASSERT(scalar_sum - entry.wnaf_skew, entry.scalar) checks whether
the first argument is non-zero (truthiness), silently ignoring the
second argument. The intent is to verify equality, so use BB_ASSERT_EQ
which actually compares the two values and reports both on failure.

Builder-only, not a constraint — no soundness impact.

Author: notnotraju

barretenberg/cpp/src/barretenberg/eccvm/precomputed_tables_builder.hpp

@@ -116,7 +116,7 @@ class ECCVMPointTablePrecomputationBuilder {
                     row.pc = entry.pc;
 
                     if (last_row) {
-                        BB_ASSERT(scalar_sum - entry.wnaf_skew, entry.scalar);
+                        BB_ASSERT_EQ(scalar_sum - entry.wnaf_skew, entry.scalar);
                     }
                     // the last element of the `precomputed_table` field of a `ScalarMul` is the double of the point.
                     row.precompute_double = entry.precomputed_table[bb::eccvm::POINT_TABLE_SIZE];