Mouse: report instantaneous cont4 deltas (bypass accumulator)

ms_present=1 is confirmed on hardware (D-pad goes dead when a USB mouse is
attached), so detection works, but the report-counter-gated accumulator never
produced movement. Report the live cont4 delta directly - same approach as the
working virtual mouse - to get the deltas through to the SNES.

Author: timboettiger

rtl/ioport.sv

@@ -90,12 +90,15 @@ wire signed [15:0] ms_dy      = MOUSE_DATA[31:16];
 // Movement accumulated between SNES polls -> sign + 7-bit magnitude
 reg  signed [15:0] ms_acc_x, ms_acc_y;
 reg         [15:0] ms_rpt_last;
-wire        [15:0] ms_absx = ms_acc_x[15] ? (~ms_acc_x + 16'sd1) : ms_acc_x;
-wire        [15:0] ms_absy = ms_acc_y[15] ? (~ms_acc_y + 16'sd1) : ms_acc_y;
+// Report the instantaneous cont4 delta directly (bypassing the accumulator and
+// the report-counter gate) — same approach as the working virtual mouse, which
+// reports the live stick deflection rather than an accumulated value.
+wire        [15:0] ms_absx = ms_dx[15] ? (~ms_dx + 16'sd1) : ms_dx;
+wire        [15:0] ms_absy = ms_dy[15] ? (~ms_dy + 16'sd1) : ms_dy;
 wire         [6:0] ms_mx   = (ms_absx > 16'd127) ? 7'd127 : ms_absx[6:0];
 wire         [6:0] ms_my   = (ms_absy > 16'd127) ? 7'd127 : ms_absy[6:0];
-wire               ms_sx   = ms_acc_x[15];
-wire               ms_sy   = ~ms_acc_y[15];
+wire               ms_sx   = ms_dx[15];
+wire               ms_sy   = ~ms_dy[15];
 
 reg joystick_detected = 0;
 reg  [1:0] speed = 0;