dsh-sleep-cycle: Sleep Cycle Bedtime Recommendations

The DeepSeek Harness plugin `dsh-sleep-cycle` implements sleep-cycle calculation in pure Node.js to provide sleep-onset suggestions for DSH sessions. With no network dependencies, it accurately computes and returns detailed results. Developers can install it using a command and directly invoke its registered tool in a session. Note that the results are estimates only and do not constitute medical advice; review the source code and license before installation.