dsh-plugin-agentcss: Add a layer of deliverable self-check to the agent's report page

The DeepSeek Harness plugin maintained by owain323 wraps the agentcss report library into four tools callable by models: `agentcss_catalog` checks component and stylesheet paths, `agentcss_new_page` generates self-contained page skeletons, `agentcss_check` performs static checks for class names, stylesheet references, alt, scope, and nesting issues, and `agentcss_pdf` exports PDFs using the local Chrome. It addresses three categories of silent failures: inventing class names, missing stylesheet references, and incorrect skeleton hierarchy. It does not include component definitions; the whitelist is calculated dynamically from the library's CSS. It supports both npm and GitHub installation methods and has been tested with Node >= 18, agentcss ^0.27.5, and Harness 0.2.x. By default, it does not overwrite existing files and does not truncate content if PDF export fails or exceeds the page count budget. It runs with the permissions of the current dsh process; users should check the source code, cordis.patch.yml patch, and MIT license before installation.