Make RUBIES a colon-delimited string instead of an array

Motivation
---
Fix chruby in Claude. Core issue is RUBIES is not set in claude shells.

Before
---
RUBIES was a bash array, and bash arrays cannot be exported. So every
fresh subshell — including every Claude Code Bash tool call — started
with an empty RUBIES and chruby failed to resolve any Ruby version,
even though RUBY_ROOT, GEM_HOME, and PATH were already set correctly
in that same subshell.

After
---
RUBIES is exported as a colon-delimited string, like PATH, so chruby
resolves correctly in any subshell, including Claude's. One side
effect: RUBIES now shows up in every child process's environment
(e.g. in `env` output), which it never did as an array.

Author: kbrock

share/chruby/chruby.sh

@@ -1,10 +1,15 @@
 CHRUBY_VERSION="0.3.9"
-RUBIES=()
+RUBIES=""
 
 for dir in "$PREFIX/opt/rubies" "$HOME/.rubies"; do
-	[[ -d "$dir" && -n "$(command ls -A "$dir")" ]] && RUBIES+=("$dir"/*)
+	if [[ -d "$dir" && -n "$(command ls -A "$dir")" ]]; then
+		for ruby in "$dir"/*; do
+			RUBIES="${RUBIES:+$RUBIES:}$ruby"
+		done
+	fi
 done
-unset dir
+unset dir ruby
+export RUBIES
 
 function chruby_reset()
 {
@@ -71,7 +76,8 @@ function chruby()
 			;;
 		"")
 			local dir ruby
-			for dir in "${RUBIES[@]}"; do
+			local IFS=:
+			for dir in $RUBIES; do
 				dir="${dir%%/}"; ruby="${dir##*/}"
 				if [[ "$dir" == "$RUBY_ROOT" ]]; then
 					echo " * ${ruby} ${RUBYOPT}"
@@ -84,7 +90,8 @@ function chruby()
 		system) chruby_reset ;;
 		*)
 			local dir ruby match
-			for dir in "${RUBIES[@]}"; do
+			local IFS=:
+			for dir in $RUBIES; do
 				dir="${dir%%/}"; ruby="${dir##*/}"
 				case "$ruby" in
 					"$1")	match="$dir" && break ;;