fix: parse private OpenClaw hook names

[steipete]

Summary

• parse the OpenClaw target hook list after its declaration became a private const
• preserve strict exported-array parsing for plugin SDK entrypoint surfaces
• cover the current as const satisfies readonly PluginHookName[] declaration shape

Proof

• npm test (206 passed)
• patched source against the current OpenClaw checkout: generated-surface check passed
• AutoReview: clean, no accepted/actionable findings