codex-plugin: stale test failure message in hooks.test.js

[chenliuyun]

Context

Follow-up from PR #73 (removes the unsupported top-level onInstall hook and hooks.json from the Codex plugin manifests).

Issue

In packages/codex-plugin/tests/hooks.test.js, the assertion for switchbot-codex-auth still has a failure message saying "so the hook command is on PATH after npm install -g" — but the hook itself was removed in PR #73. The message is now inaccurate/stale.

Suggested fix

Update the assertion message to reflect that switchbot-codex-auth remains as a legacy/manual setup helper, not a hook, e.g.:

switchbot-codex-auth must remain available as a legacy/manual setup helper

Acceptance criteria

• Assertion message in hooks.test.js no longer references the removed hook/PATH behavior
• Tests still pass