revert: use safe parameter checks in bash/zsh init for set -u compatibility

Author: Copilot

src/shell/scripts/omp.bash

@@ -116,7 +116,7 @@ function _omp_hook() {
     _omp_stack_count=$((${#DIRSTACK[@]} - 1))
 
     _omp_execution_time=-1
-    if [[ -n "${_omp_start_time+x}" ]]; then
+    if [[ $_omp_start_time ]]; then
         local omp_now=$("$_omp_executable" get millis)
         _omp_execution_time=$((omp_now - _omp_start_time))
         _omp_no_status=false

src/shell/scripts/omp.zsh

@@ -63,7 +63,7 @@ function _omp_precmd() {
   _omp_no_status=true
   _omp_tooltip_command=''
 
-  if [ -n "${_omp_start_time+x}" ]; then
+  if [ $_omp_start_time ]; then
     local omp_now=$($_omp_executable get millis)
     _omp_execution_time=$(($omp_now - $_omp_start_time))
     _omp_no_status=false