shell: bash readline prefix history search via XDG inputrc

Add $INPUTRC pointing at ~/.config/readline/inputrc and ship that file
with history-search Up/Down bindings (cursor to end), mirroring zsh's
history-beginning-search-end. zsh ignores readline, so this is bash-side
only. Includes /etc/inputrc to keep distro defaults.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

shell/.config/readline/inputrc

@@ -0,0 +1,13 @@
+# Readline config (bash line editing + any readline program: python, psql...).
+# Set via $INPUTRC; see shell/exports. zsh ignores this (uses ZLE); its
+# equivalent prefix-search bindings live in zsh/.zshrc.
+#
+# Pull in distro defaults; a custom INPUTRC otherwise replaces them entirely.
+$include /etc/inputrc
+
+# zsh-style prefix history search: type a prefix, Up/Down walk matching
+# history entries with cursor at end of line. Empty prefix = previous/next.
+"\e[A": history-search-backward
+"\e[B": history-search-forward
+"\eOA": history-search-backward
+"\eOB": history-search-forward

shell/.config/shell/exports

@@ -33,5 +33,8 @@ export PYTHON_HISTFILE="${XDG_CACHE_HOME:-$HOME/.cache}/python/history"
 # Wget config file
 export WGETRC="${XDG_CONFIG_HOME:-$HOME/.config}/wget/rc"
 
+# Readline config file (bash line editing + any readline program)
+export INPUTRC="${XDG_CONFIG_HOME:-$HOME/.config}/readline/inputrc"
+
 # NOTE: ZDOTDIR lives in ~/.zshenv, not here. It must be set before zsh reads
 # any rc file, and this file is sourced too late for that.