fix(editor): prevent UI redraw conflicts during editor suspend/resume

Guard against re-entrant editor launches, abort editor on Ctrl-Z,
and centralize suspend-aware redraws through prof_doupdate() to prevent
terminal corruption when SIGTSTP is received while editor is active.

Removes SIGUSR1 editor escape in favor of standard pkill <editor> recovery.

src/command/cmd_defs.c

@@ -2638,7 +2638,8 @@ static const struct cmd_t command_defs[] = {
       CMD_DESC(
               "Spawn external editor to edit message. "
               "After editing the inputline may appear empty. Press enter to send the text anyways. "
-              "Use /executable to set your favourite editor." )
+              "Use /executable to set your favourite editor. "
+              "Ctrl-Z in the editor aborts the session and returns to Profanity." )
     },
 
     { CMD_PREAMBLE("/correct-editor",