refactor: extend source_file with optional export mode for ~/.env

Add 'export' flag to source_file that wraps the source call in set -a/+a,
auto-exporting all variables to child processes. Use it for ~/.env instead
of a separate inline block.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.zshrc

@@ -28,12 +28,16 @@ add_to_path() {
 }
 
 # Source a file with existence and readability check (zsh-friendly)
-# Usage: source_file /path/to/file
+# Usage: source_file /path/to/file [export]
+# Pass 'export' as second arg to auto-export all variables via set -a/+a.
 source_file() {
   local file="$1"
+  local export_vars="${2:-}"
 
   if [[ -f "$file" && -r "$file" ]]; then
+    [[ "$export_vars" == "export" ]] && set -a
     source "$file"
+    [[ "$export_vars" == "export" ]] && set +a
   fi
 }
 
@@ -83,19 +87,6 @@ for expr in "${eval_expressions[@]}"; do
 done
 
 
-# =============================================================================
-# ENVIRONMENT VARIABLES
-# =============================================================================
-
-# Source ~/.env with set -a so every variable is automatically exported
-# and inherited by child processes (scripts, subshells, etc.).
-if [[ -f "$HOME/.env" && -r "$HOME/.env" ]]; then
-  set -a
-  source "$HOME/.env"
-  set +a
-fi
-
-
 # =============================================================================
 # CONFIGURATION FILES TO SOURCE
 # =============================================================================
@@ -108,6 +99,9 @@ source_files=(
   "$HOME/.p10k.zsh"
 )
 
+# Source ~/.env with auto-export so variables reach child processes
+source_file "$HOME/.env" export
+
 # Source zsh-compatible files (skip if missing, no warnings)
 for config_file in "${source_files[@]}"; do
   source_file "$config_file"