fix: support renamed Codex hooks feature

[Inference1]

Summary

• detect the current hooks feature while retaining compatibility with legacy codex_hooks
• use the detected feature name when enabling hooks and disabling hooks for nested Codex calls
• update the Codex install guide and add regression coverage for current, legacy, dual-name, and unsupported feature sets
• keep empty nested-hook argument arrays safe on Bash 3.2

Testing

• bash tests/test-codex-hooks-feature.sh
• bash tests/test-codex-hook-install.sh
• bash tests/test-bitlesson-select-routing.sh
• bash tests/test-disable-nested-codex-hooks.sh
• bash tests/test-agent-teams.sh
• bash -n on all changed shell scripts
• isolated real-CLI dry run confirmed DRY-RUN enable hooks feature

Fixes #208

[Inference1]

@tony-nowatzki Would you please review this pr?