use d=I for kitty SPRIXEL_HIDE to kill cache

TERMINALS.md

@@ -266,6 +266,8 @@ are best avoided until the problems are better understood:
    bound to up to three digits, which ought be drawn inside.
 * '࣢' U+08E2 ARABIC DISPUTED END OF AYAH
 * '﷽' U+FDFD ARABIC LIGATURE BISMILLAH AR-RAHMAN AR-RAHEEM
+* '⁄' U+2044 [FRACTION SLASH](https://en.wikipedia.org/wiki/Universal_Character_Set_characters#Fraction_slash)
+   bound to digits fore and aft
 
 ## Notes for terminal authors
 

src/lib/kitty.c

@@ -1117,7 +1117,7 @@ int kitty_blit_selfref(ncplane* n, int linesize, const void* data,
 
 int kitty_remove(int id, fbuf* f){
   loginfo("Removing graphic %u\n", id);
-  if(fbuf_printf(f, "\e_Ga=d,d=i,i=%d\e\\", id) < 0){
+  if(fbuf_printf(f, "\e_Ga=d,d=I,i=%d\e\\", id) < 0){
     return -1;
   }
   return 0;

src/lib/notcurses.c

@@ -2146,6 +2146,7 @@ void ncplane_yx(const ncplane* n, int* y, int* x){
   }
 }
 
+// special case of ncplane_erase_region()
 void ncplane_erase(ncplane* n){
   loginfo("erasing plane\n");
   if(n->sprite){