dsh-custom-header: DeepSeek Harness Request Header Modification and Identity Spoofing Plugin

`dsh-custom-header` is a DeepSeek Harness (DSH) plugin designed to intercept and modify HTTP requests at the transport layer, simulate specific client behavior, and bypass risk control. It supports injecting custom headers (such as User-Agent and Session ID), stripping SDK fingerprints, rewriting URLs, and patching Anthropic request bodies. It also provides session isolation and 403 diagnostics. Users can select a preset profile via configuration files or the DSH settings interface, or control it dynamically using the JS API. The installation command is `dsh plugin --profile web add dsh-custom-header`.