dsh-session-archive-plugin: DSH Context Archiving and History Retrieval Plugin

The `dsh-session-archive-plugin` plugin for DeepSeek Harness (DSH) addresses context space limitations in long conversations. It prevents the loss of historical dialogue caused by compression by archiving sessions and supporting full-text search. After installation, `dsh web` must be restarted. It provides the `archive_session` (archive a session) and `search_archive` (search history) tools, along with the `session-archive` skill. Installation requires a Python environment and supports overriding default parameters via a configuration file.