Add negative-min unbounded test for line coverage

test_regress/t/t_property_sexpr_range_delay_bad.out

@@ -20,4 +20,8 @@
                                                   : ... note: In instance 't'
    30 |   a5: assert property (@(posedge clk) a |-> ##[cyc:$] b);
       |                                             ^~
+%Error: t/t_property_sexpr_range_delay_bad.v:34:45: Range delay bounds must be non-negative (IEEE 1800-2023 16.7)
+                                                  : ... note: In instance 't'
+   34 |   a6: assert property (@(posedge clk) a |-> ##[NEG:$] b);
+      |                                             ^~
 %Error: Exiting due to

test_regress/t/t_property_sexpr_range_delay_bad.v

@@ -29,4 +29,8 @@ module t;
   // Non-constant minimum in unbounded range
   a5: assert property (@(posedge clk) a |-> ##[cyc:$] b);
 
+  // Negative minimum in unbounded range
+  localparam int NEG = -1;
+  a6: assert property (@(posedge clk) a |-> ##[NEG:$] b);
+
 endmodule