purge all references to nccell_{set}?_[fb]channel() #2571

USAGE.md

@@ -2249,18 +2249,6 @@ Helpers are provided to manipulate an `nccell`'s `channels` member. They are
 all implemented in terms of the lower-level [Channels API](#channels).
 
 ```c
-// Extract the 32-bit background channel from a cell.
-static inline uint32_t
-nccell_bchannel(const nccell* cl){
-  return ncchannels_bchannel(cl->channels);
-}
-
-// Extract the 32-bit foreground channel from a cell.
-static inline uint32_t
-nccell_fchannel(const nccell* cl){
-  return ncchannels_fchannel(cl->channels);
-}
-
 // Extract 24 bits of foreground RGB from 'cl', shifted to LSBs.
 static inline uint32_t
 nccell_fg_rgb(const nccell* cl){

doc/man/man3/notcurses_cell.3.md

@@ -78,14 +78,6 @@ typedef struct nccell {
 
 **char* nccell_extract(const struct ncplane* ***n***, const nccell* ***c***, uint16_t* ***stylemask***, uint64_t* ***channels***);**
 
-**uint32_t nccell_bchannel(const nccell* ***c***);**
-
-**uint32_t nccell_fchannel(const nccell* ***c***);**
-
-**uint64_t nccell_set_bchannel(nccell* ***c***, uint32_t ***channel***);**
-
-**uint64_t nccell_set_fchannel(nccell* ***c***, uint32_t ***channel***);**
-
 **uint32_t nccell_fg_rgb(const nccell* ***c***);**
 
 **uint32_t nccell_bg_rgb(const nccell* ***c***);**