dsh-codex-file-panel: Add a Codex-style workspace file sidebar to DeepSeek Harness Web UI

# Introduction When developing agents with DeepSeek Harness (DSH), the Web UI is the standard entry point. However, tasks such as viewing and modifying workspace files, reviewing Git changes, or launching a temporary terminal often require toggling between the browser, editor, and terminal, resulting in fragmented context. dsh-codex-file-panel addresses this issue by consolidating the file tree, search, editing, preview, and Git review into the right-side panel of the Web UI, while also adding capabilities closely tied to file workflows, such as a bottom terminal. The following sections introduce the features, installation, configuration, and security boundaries in order. # What is it? dsh-codex-file-panel is a community plugin maintained by JesonChou for DSH.