feat(rc): Unify history tool selection (atuin/mcfly) with preference order

Merge rc.d/mcfly and rc.d/atuin into rc.d/history, following the same
preference-list + availability-check + fallback pattern as rc.d/prompt,
so only one history tool is active at a time instead of both being
initialized independently. Also normalize variable expansions in
rc.d/prompt to consistently use ${var} braces.

rc.d/history

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+# Customize shell history search
+
+# Indicate your preference order for history tools
+# The first one found available will be used
+MY_HISTORY_TOOLS="atuin mcfly"
+
+for tool in ${MY_HISTORY_TOOLS}; do
+	if (command -v "${tool}" &>/dev/null); then
+		USE_HISTORY_TOOL="${tool}"
+		break
+	fi
+done
+
+case "${USE_HISTORY_TOOL}" in
+
+# https://atuin.sh/
+"atuin")
+	if (command -v atuin &>/dev/null); then
+		eval "$(atuin init bash)"
+	else
+		echo "${USE_HISTORY_TOOL} command not found"
+	fi
+	;;
+
+# https://github.com/cantino/mcfly
+"mcfly")
+	if (command -v mcfly &>/dev/null); then
+		export MCFLY_PROMPT="❯ "
+		export MCFLY_INTERFACE_VIEW=BOTTOM
+		export MCFLY_RESULTS=50
+		export MCFLY_RESULTS_SORT=LAST_RUN
+		# export MCFLY_KEY_SCHEME=vim
+		export MCFLY_FUZZY=3
+		eval "$(mcfly init bash)"
+	else
+		echo "${USE_HISTORY_TOOL} command not found"
+	fi
+	;;
+
+*)
+	# Default sane bash history behavior
+	export HISTCONTROL=ignoreboth:erasedups
+	export HISTSIZE=10000
+	export HISTFILESIZE=20000
+	shopt -s histappend
+	;;
+
+esac

rc.d/mcfly

@@ -1,11 +0,0 @@
-#!/bin/bash
-
-if (command -v mcfly &>/dev/null); then
-  export MCFLY_PROMPT="❯ "
-  export MCFLY_INTERFACE_VIEW=BOTTOM
-  export MCFLY_RESULTS=50
-  export MCFLY_RESULTS_SORT=LAST_RUN
-  # export MCFLY_KEY_SCHEME=vim
-  export MCFLY_FUZZY=3
-  eval "$(mcfly init bash)"
-fi

rc.d/prompt

@@ -4,11 +4,11 @@
 
 # Indicate your preference order for prompt tools
 # The first one found available will be used
-MY_PROMPTS="starship powerline-go"
+MY_PROMPT_TOOLS="starship powerline-go"
 
-for prompt in $MY_PROMPTS; do
-	if (command -v "$prompt" &>/dev/null); then
-		USE_PROMPT="$prompt"
+for prompt in ${MY_PROMPT_TOOLS}; do
+	if (command -v "${prompt}" &>/dev/null); then
+		USE_PROMPT="${prompt}"
 		break
 	fi
 done
@@ -30,7 +30,7 @@ case "${USE_PROMPT}" in
 		function _update_ps1() {
 			PS1=$(powerline-go -jobs "$(jobs -p | wc -l)" -error $? -modules "ssh,host,wsl,user,cwd,direnv,venv,perms,git,jobs,exit,root" -modules-right "docker,docker-context,kube,terraform-workspace,termtitle" -newline)
 		}
-		if [ "$TERM" != "linux" ]; then _prompt_command_add "_update_ps1"; fi
+		if [ "${TERM}" != "linux" ]; then _prompt_command_add "_update_ps1"; fi
 	else
 		echo "${USE_PROMPT} command not found"
 	fi
@@ -38,7 +38,7 @@ case "${USE_PROMPT}" in
 
 *)
 	# Default simple prompt
-	if [ "$UID" -eq 0 ]; then
+	if [ "${UID}" -eq 0 ]; then
 		export PS1='\[\e[01;31m\]\u@\h\[\e[01;34m\] \w \$\[\e[0m\] '
 	else
 		export PS1='\[\e[01;32m\]\u@\h\[\e[01;34m\] \w \$\[\e[0m\] '