dsh-purge-archived: Purge archived conversations in DeepSeek Harness.

DSH's archiving only creates a marker; logs remain on the disk forever. trimine's `dsh-purge-archived` (admin-security, v1.0.1, MIT) fills this missing operation: permanently delete archived sessions. A single purge clears session logs, projection cache checkpoints, archive markers, and workspace member records. It also provides a sidebar cleanup panel, batch deletion, and one-click cleanup for invalid entries marked as "logs lost". It only accepts IDs from the archive collection or pure registry remnants; conversations that are not archived but still have logs are rejected. The HTTP route only accepts same-origin JSON POST requests. Install using `dsh plugin --profile desktop add dsh-purge-archived`. Uninstall runs with the current DSH process permissions. It is recommended to review the source code and license before installation.