dsh-day-of-year: Calculate the Day of the Year

The DeepSeek Harness (DSH) plugin `dsh-day-of-year` is designed to allow agents to locally calculate the ordinal day number of the current date within a year without requiring internet access. Maintained by user `uckkk` and implemented in pure Node.js, it is a basic utility in the DSH ecosystem. The installation command is `dsh plugin add github:uckkk/dsh-day-of-year`. It is suitable for scenarios involving date-based periodic statistics or logical judgments, requires specific PeerDependencies versions, and users are advised to review the source code before installation to ensure security.