dsh-agents-viewer: Display the AGENTS.md instruction chain in the DSH right sidebar

dsh-agents-viewer is a DSH dual-face bundle plugin maintained by atrestandbed-bot (v0.7.0, MIT) that enables viewing and editing global, shared, and project-level AGENTS.md files via a native tab in the right sidebar. It provides a one-click button in the chat header and a command-line `/agents` interface that operates independently of the UI. The host retrieves the workspace based on sessionId, and file writing is performed via a directory whitelist. If DSH renames or removes a service, it only loses one entry point without affecting startup. The text provides a three-step manual installation process, usage for `adapt`, `adapt:install`, and `check-compat`, and explains limitations such as saving not triggering hot reload and `/agents o|c` requiring a restart to take effect.