dsh-testkit: The Real Host Release Barrier for the DeepSeek Harness Plugin

# Introduction In DSH's "everything is a plugin" development paradigm, the pitfalls most easily encountered by plugin authors often lie outside the compilation phase: while build artifacts compile and unit tests pass, the plugin may fail after release due to missing files in the tarball, bundle registration failures within the host, or profile corruption during uninstallation. The commonality among these issues is that they only manifest between the "packaging artifact actually installed by the user" and the "real host," a gap that local static checks cannot cover. dsh-testkit fills this gap by taking the artifact generated via `npm pack` and placing it into a precisely specified real DSH host, executing the complete lifecycle, and leaving evidence for maintainers to review. # What is this [iiwish/dsh-testkit](https://g