index: guard the $in cartesian cap against u64 overflow; drop debug print

src/index.zig

@@ -706,6 +706,9 @@ fn evaluate_index(gpa: std.mem.Allocator, ix: *const Index, clauses: []const Cla
     }
     var combos: u64 = 1;
     for (0..run) |i| {
+        // A single huge $in list (or a product over 100) falls back to a
+        // scan; checking the factor first keeps the product from wrapping.
+        if (counts[i] > max_combos) return null;
         combos *= counts[i];
         if (combos > max_combos) return null;
     }