home: zsh: use terminfo for mappings

home/zsh/extra-mappings.zsh

@@ -1,5 +1,13 @@
+# shellcheck disable=2154
+
+# The expression: (( ${+terminfo} )) should never fail, but does if we
+# don't have a tty, perhaps due to a bug in the zsh/terminfo module.
+if [[ "$TERM" != emacs ]] && (( ${+terminfo} )) 2>/dev/null; then
     # Fix delete key not working
-bindkey "\e[3~" delete-char
+    ((${+terminfo[kdch1]})) && bindkey -- "${terminfo[kdch1]}" delete-char
+    # Enable Shift-Tab to go backwards in completion list
+    ((${+terminfo[kcbt]})) && bindkey -- "${terminfo[kcbt]}" reverse-menu-complete
+fi
 
 # Fix Ctrl+u killing from the cursor instead of the whole line
 bindkey '^u' backward-kill-line