dsh-guardwall: Runtime Safety Guardrails for DeepSeek Harness

`dsh-guardwall` is a security plugin for DeepSeek Harness (DSH), designed to protect the plugin ecosystem with a two-layer defense mechanism. Before installation, it performs a health check on plugins using static scanning, permission manifests, and trust scoring; at runtime, it blocks high-risk operations such as destructive commands, credential leakage, SSRF, and reverse shells without relying on third-party dependencies. Additionally, the plugin supports hot-loading of rules and uses HMAC chained hashing to ensure the integrity of audit logs, providing end-to-end security assurance for the Agent execution environment.