dsh-workspace-purge: Permanently delete left-side chat and workspace

Deletion in the DSH sidebar is archiving, while workspace deletion only deregisters. Since logs and projection cache remain on the disk, the sidebar becomes increasingly cluttered. `dsh-workspace-purge`, maintained by xuenann and categorized under "Memory", deletes session logs, projection cache, and workspace registrations together, and allows workspace directories to be moved to the Recycle Bin. It provides three entry points: the Delete Data Panel at the bottom of the sidebar, the single-chat menu, and the `workspace_purge` agent tool; the currently active conversation will be rejected for deletion. Windows has a Recycle Bin fallback, while other platforms perform direct permanent deletion. It is currently not yet registered in the `awesome-dsh-plugin` registry and must be installed via `dsh plugin --profile desktop add` after running `npm pack`. The plugin does not connect to the internet, does not collect telemetry, operates exclusively on four paths within `DSH_HOME`, and is licensed under the MIT License.