dsh-svn-plugin: SVN Version Control Panel for DeepSeek Harness

`dsh-svn-plugin` is an SVN management plugin designed specifically for DeepSeek Harness. By injecting a dedicated tab into the right sidebar of `dsh-better-sidebar`, it provides a web-based SVN workflow experience consistent with the Git panel. The plugin supports core workflows including viewing local modifications, committing updates, comparing code, viewing history, shelving management, conflict resolution, code annotations, branch switching, and repository browsing. It also injects tools such as `svn_status` into the Agent, and supports grouped commits and property management. Installation requires DSH 0.1.0-rc.8+ and `dsh-better-sidebar` ≥ 0.14.0. Note that the shelving feature depends on the system SVN client supporting s.