Fix bash 3.2 empty-array crash that aborts hooks under set -u

[chhzh123]

On macOS (bash 3.2.57, the system default) expanding a bare "${arr[@]}" on an empty array under set -u is a fatal "unbound variable" error, not the no-op it is on bash >= 4.4. The RLCR hooks run under set -euo pipefail and source these files, so that abort exits the hook with a non-zero, non-blocking status and no stderr -- surfaced by Claude Code as "Stop hook error: Failed with non-blocking status code: No stderr output", firing on every Stop-hook invocation.

Two empty-able array expansions hit this:

• hooks/lib/template-loader.sh: render_template() runs env "${env_vars[@]}" awk ...; env_vars is empty for every static block/status/completion message (no substitution vars), so the Stop hook crashed before Codex even ran.
• hooks/loop-codex-stop-hook.sh: CODEX_DISABLE_HOOKS_ARGS is initialized empty and only filled when the installed Codex CLI supports --disable; on older Codex builds it stays empty, so the codex review/codex exec invocations crashed the same way.

Guard each with the portable ${arr[@]+"${arr[@]}"} idiom (expand to the quoted elements when non-empty, to nothing when empty), correct on bash 3.2 and >= 4.4 alike. Other "${arr[@]}" expansions in the hooks iterate hardcoded non-empty literals and are unaffected.

Reproduced on /bin/bash 3.2.57:

  set -euo pipefail; a=(); env "${a[@]}" true         # -> a[@]: unbound variable (exit 1)
  set -euo pipefail; a=(); env ${a[@]+"${a[@]}"} true # -> ok (exit 0)