dsh-rayburst: Offloading DSH downloads to the Rayburst engine

dsh-rayburst is a DSH plugin maintained by cat-Logan that redirects downloads within the plugin to Rayburst (the aria2-next kernel) rather than having the model stream bytes directly in the process. Upon installation, it provides three tools—rayburst_download, rayburst_wait, and rayburst_status—responsible for initiating disk downloads (returning status, byte count, path, and SHA256), resuming tasks by GID, and querying task status, respectively. By default, it reads the RPC secret and listening port from Rayburst's own aria2.conf, though these can be overridden using environment variables; if not configured, it searches common paths sequentially. The plugin will explicitly report an error if the engine cannot be reached rather than failing silently. Installation is done via `dsh plugin --profile web add <local directory>` (or by selecting the local directory in the plugin management interface), followed by restarting DSH; it includes a self-test script (`verify/verify-host.mjs`) performing 10 assertions. The plugin only registers tools and does not modify the DSH core; it is licensed under the MIT license. It does not intercept web content scraping by `web_fetch`, nor does it inject cookies for internal network or login-state downloads. For large files that remain unfinished within the wait budget, it returns `status: active`, allowing repeated calls to `rayburst_wait`. It runs with the permissions of the current DSH process; reviewing the source code and license is recommended before installation.