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

src/commands.zig

@@ -1889,7 +1889,6 @@ test "indexed queries are equivalent to scans over a mixed corpus" {
         clear_id_list(testing.allocator, &scanned);
         try dispatch_find_ids(&tdb, io, "eq", f.pairs, &scanned);
         const indexed = indexed_results.items[fi];
-        if (scanned.items.len != indexed.items.len) std.debug.print("MISMATCH(ab) filter {d}: scan={d} idx={d}\n", .{ fi, scanned.items.len, indexed.items.len });
         try testing.expectEqual(scanned.items.len, indexed.items.len);
         for (scanned.items, indexed.items) |a, b| try testing.expectEqualSlices(u8, a, b);
     }

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;
     }