shl-session-history: Mini Slider for Session History Requests

`shl-session-history` is a DeepSeek Harness (DSH) plugin designed to address the pain point of locating early requests in long conversations. It provides a mini slider rail on the left side of the chat area, allowing users to view summaries by hovering and jump to specific conversations by clicking, while automatically handling pagination loading. It features highly customizable styling, real-time updates, smart filtering, and automatic hiding. Version 1.1.5 refactors the positioning mechanism, ensuring precise jumps via direct links using unique keys. Users can install it with a terminal command and adjust its appearance and size in the settings.