dsh-agents-md-editor: View and Save AGENTS.md in the Left Sidebar

AikawaNaya's DSH client bundle features an edit panel for `~/.dsh/AGENTS.md` opened in the left sidebar of the Web UI. The page polls the file's SHA1 version every 2 seconds; it automatically syncs external changes when the buffer is clean and prompts not to overwrite if there are unsaved changes. Saving is handled by `/agents-md-editor/api/save`, carrying the version number loaded at startup, and returns a 409 conflict if the file changes midway. Writing to disk involves creating a temporary file first and then renaming it to prevent leaving truncated files in case of a crash. Switching panels does not lose drafts, and the font size is read from theme variables. Installation is done via `dsh plugin --profile desktop add dsh-agents-md-editor`, with `filePath` as the only configuration option, defaulting to `~/.dsh/AGENTS.md`. Both routes pass the browser trust barrier and do not accept path parameters, restricting access to the configured file. On the Host side, `node:fs` is used for direct writing because the target lies outside the session workspace and UI actions lack an approval channel. The component requires Node.js >= 22, includes 22 test checks, does not touch real files, and is licensed under MIT. The plugin runs with the privileges of the current dsh process; users should read the source code and check the license before installing.