dsh-config-watch: Record DSH environment configuration change history

dsh-config-watch is a DeepSeek Harness plugin maintained by Equinox7379, licensed under the MIT license, designed to address the challenge of tracking environment configuration changes. Adhering to the "everything is a plugin" philosophy, this plugin captures snapshots of critical profile files and the plugin manifest at every service start. By comparing these snapshots with the previous ones and recording the differences in a change log, it offers a clear timeline of environment configuration changes. Its core functions include recording change history and providing a `config_changes` query tool, which supports setting the `limit` parameter (default 20, max 200) to retrieve recent records. The plugin features zero dependencies, no custom session events, and no HTTP routes, with data storage limited to `~/.dsh/config-watch`.