dsh-shipcheck: An Evidence-Driven Frontend Release Checker

`dsh-shipcheck` is a frontend release-checking plugin for DeepSeek Harness (DSH), designed to replace subjective judgment with evidence-first deterministic checks. The plugin uses a real browser to generate screenshots, named baselines, and JSON reports, covering accessibility, structure, content quality, and runtime error checks. It provides tools such as `shipcheck_run` and `shipcheck_matrix` for URL checks, structural regression comparisons, and user journey simulation. Acting as a release gate, it provides reproducible failure evidence and supports quality control before manual review, though it should be noted that it is structure-based rather than pixel-level.