dsh-workflow-templates: A Built-in Workflow Template Library for DeepSeek Harness

The `workflow` tool provided by DSH lacks out-of-the-box templates. The `dsh-workflow-templates` plugin includes 12 reusable script templates and provides four core tools—list, search, run, and validate—as well as static validation. It aligns with the official contract without restricting computed return values, aiming to lower the barrier to orchestration. The plugin is installed via `cordis.yml` and supports mounting in either published or development mode. Templates can be listed, searched, or validated using the tools; `wf_template_run` only generates an invocation starting point for the official `workflow` to execute, and does not automatically run scripts.