Fix bottom panel vertical offset, enable TSU sprites in text mode

Bottom control panel sat a couple pixels too low relative to the top
panel (pre-existing, not a session regression) - nudged GYOFFSL in
int_text_off from 47+240-1 to 47+240. Confirmed correct on hardware.

Also uncommented the TSU_SEN write in int_text_on so hardware sprites
(mouse cursor) are enabled during text mode too, not just graphics
mode. Doesn't fix the known cursor clip right above the bottom panel
(that appears tied to a fixed screen row, independent of panel
position or this bit - left as a known issue, documented in README).

zifi.asm

@@ -2203,9 +2203,9 @@ txt_border	ld a,#f0
 		ld b,high VCONFIG
 		ld a,VID_TEXT+VID_320X240
 		out (c),a
-;		ld b,high TSCONFIG
-;		ld a,TSU_SEN
-;		out (c),a
+		ld b,high TSCONFIG
+		ld a,TSU_SEN
+		out (c),a
 		ld b,high VPAGE
 		ld a,Text_page
 		out (c),a
@@ -2249,7 +2249,7 @@ int_text_off	push af,hl,de,bc,ix,iy
 		push af
 		exa
 		call set_256c_mode
-		ld hl,47+240-1
+		ld hl,47+240	; was 47+240-1 - bottom panel sat a couple pixels too low
 		ld b,high GYOFFSL
 		out (c),l
 		inc b
@@ -3479,7 +3479,7 @@ status_icon_copy
 cancel_icon_copy
 		db #1a,low cancel_icon
 		db #1b,high cancel_icon
-		db #1c,2 
+		db #1c,2
 		db #1d,4+4+128
 		db #1e,#3e-2
 		db #1f,Vid_page+8