DSH Header Injection Plugin: Inject Request Headers Based on Host Rules

This plugin is maintained by ZhiGangCai and designed to enable domain-based request header injection for DeepSeek Harness (DSH). Implemented by patching the global fetch, it supports injecting headers according to Host rules and overriding same-named headers. The default preset rules can bypass AgentRouter WAF checks. The plugin supports both a visual settings panel and command-line configuration, can be installed via `dsh plugin`, and requires a Web backend restart after enabling. After installation, run `dsh-header-injection` to view rule status and hit counts.