feat: add shell profiles for zsh, sh, csh/tcsh

- profile.bash: simplified preexec_init (early return), extracted
  ___keep_complete helper for @/@@ completion wrappers
- profile.zsh: add-zsh-hook preexec, wrapper function, @/@@ aliases,
  completions via compdef
- profile.sh: POSIX-compatible for sh/dash/ksh. Wrapper function,
  @/@@ aliases. No preexec or completions.
- profile.csh: alias-based keep wrapper, @/@@ aliases. No preexec
  or completions.
- modulefile: adds KEEP_SH_PROFILE, KEEP_ZSH_PROFILE, KEEP_CSH_PROFILE
- README: updated Shell Integration table and Shell Completion section

profile.bash

@@ -6,18 +6,10 @@ function __keep_preexec {
 }
 
 function __keep_preexec_init {
-  local found=false
-  local f
   for f in "${preexec_functions[@]}"; do
-    if [[ $f = __keep_preexec ]]; then
-      found=true
-      break
-    fi
+    [[ $f = __keep_preexec ]] && return
   done
-
-  if [[ $found = false ]]; then
-    preexec_functions+=(__keep_preexec)
-  fi
+  preexec_functions+=(__keep_preexec)
 }
 
 function keep {
@@ -43,17 +35,15 @@ function @@ {
 # Shell completions
 . <(command keep --generate-completion bash)
 
-___keep_save_completion() {
-    COMP_WORDS=(keep --save "${COMP_WORDS[@]:1}")
+___keep_complete() {
+    local mode="$1"
+    COMP_WORDS=(keep "$mode" "${COMP_WORDS[@]:1}")
     COMP_CWORD=$((COMP_CWORD + 1))
     _keep
 }
 
-___keep_get_completion() {
-    COMP_WORDS=(keep --get "${COMP_WORDS[@]:1}")
-    COMP_CWORD=$((COMP_CWORD + 1))
-    _keep
-}
+___keep_save_completion() { ___keep_complete --save; }
+___keep_get_completion() { ___keep_complete --get; }
 
 complete -F ___keep_save_completion @
 complete -F ___keep_get_completion @@