fix(hooks): use printf -v for bash 3.2 compat (declare -g is 4.2+)

macOS ships /bin/bash 3.2 and the script uses #!/bin/bash with
set -euo pipefail, so declare -g would abort the SessionStart hook
with "invalid option" on every Mac. printf -v writes via assignment
semantics (global from inside a function on 3.2+) — same scope
outcome, broader compatibility.

hooks/scripts/check-config.sh

@@ -37,7 +37,9 @@ load_env_vars() {
       # command substitution in backtick-containing comments
       value="${value%%[[:space:]]#*}"
       if [[ -n "$key" && -n "$value" ]]; then
-        declare -g "ENV_${key}=${value}"
+        # printf -v writes via assignment semantics (global from inside a
+        # function), works on macOS's /bin/bash 3.2 — `declare -g` is 4.2+.
+        printf -v "ENV_${key}" '%s' "$value"
       fi
     done < "$file"
   fi