DeepSeek Harness Plugin: dsh-tgrep

`dsh-tgrep` is a code search plugin for DeepSeek Harness, designed to address the high query latency of the default `grep` tool in large codebases. It leverages Microsoft's `tgrep` engine, replacing built-in tools via trigram indexing and Agent-plane shadowing to significantly improve search speed without modifying model presets. The plugin features automatic daemon operation, graceful degradation (falling back to `grep` mode when no index is available), and zero runtime dependencies. To use it, ensure the environment includes the `tgrep` binary and observe large-file limits and index-building requirements.