dsh-session-toc: Add a right-side TOC sidebar for the DeepSeek Harness Web UI session page

# Preface Long conversations have a specific inconvenience in the DSH Web UI: the session view is loaded on demand, and early messages are not in memory by default. To return to a previous question, you can only repeatedly click "Load Earlier" or scroll through the entire list to find the location. The longer the conversation, the more inefficient this action becomes. The DeepSeek official website features a table of contents index on the right side; clicking on it jumps to the corresponding content. `dsh-session-toc` replicates this experience within the DeepSeek Harness Web UI. Below is an introduction to the plugin's features, installation, and usage details. # What is it? `dsh-session-toc` (repository `notload/dsh-session-toc`) is maintained by notload.