revert(shell): move iris integration to the iris branch

Reverts 43dfe48, 0692ae3, e0cdcd6 and the cable-description half of
098da70 (the star-prompt stats stay). master returns to the pre-iris
shell setup: atuin in fish/zsh/bash, the down -> pj binding with
PJ_QUIET, and the fish/zsh key bindings as they were. The iris work
lives on the `iris` branch.

dot_config/bash/keybinds.bash

@@ -1,7 +1,7 @@
 # ~/.config/bash/keybinds.bash — readline ports of the television keys in
 # fish_user_key_bindings.fish / zsh keybinds.zsh:
 #   ctrl-o → gho (ghq-repos cable, cd)     ctrl-e → tv git-files (nvim)
-#   ctrl-p → pj (pj cable)
+#   ctrl-p → pj (pj cable)                 down   → pj on an empty prompt
 #   ctrl-t → tv smart autocomplete (tv init bash ships no ctrl-t)
 # Keys owned by kitty.conf never reach the shell: ctrl-h/j/k/l (pass_keys.py).
 #
@@ -19,12 +19,12 @@ _kb_git_files() {
 }
 bind -x '"\C-e": _kb_git_files'
 
-# ctrl-p. pj reports through $PJ_STATE: `open` = cancelled, `ran` = a task
-# printed output, empty = no task sources.
+# ctrl-p, and down on an empty prompt. pj reports through $PJ_STATE: `open`
+# = cancelled, `ran` = a task printed output, empty = no task sources.
 _kb_pj() {
     local state
     state=$(mktemp) || return
-    PJ_STATE=$state pj </dev/tty
+    PJ_STATE=$state pj "$@" </dev/tty
     [ "$(<"$state")" = open ] && _kb_up
     rm -f "$state"
 }
@@ -66,6 +66,21 @@ bind -x '"\C-x1": _kb_gho'
 bind -x '"\C-x0": _kb_restore'
 bind '"\C-o": "\C-x1\C-x2\C-x3\C-x0"'
 
+# down: the pj cable on an idle, empty prompt, otherwise history search
+# (fish's _pj_bind_down). bind -x can't call readline functions, so _kb_down
+# rebinds \C-x5, which the macro sends right after it.
+_kb_down() {
+    if [ -n "$READLINE_LINE" ]; then
+        bind '"\C-x5": history-search-forward'
+        return
+    fi
+    PJ_QUIET=1 _kb_pj
+    bind '"\C-x5": redraw-current-line'
+}
+bind -x '"\C-x4": _kb_down'
+bind '"\e[B": "\C-x4\C-x5"'
+bind '"\eOB": "\C-x4\C-x5"'
+
 # ctrl-t: pick with the channel tv guesses from the text left of the cursor
 # (shell_integration.channel_triggers) and insert the picks there, quoted.
 _kb_tv_autocomplete() {