dsh-session-workbench: Make historical sessions searchable and retrievable

# Introduction After using DeepSeek Harness (dsh) for some time, historical sessions tend to pile up. You might have fine-tuned an MCP config or settled on a solution in a session, but days later, when you want to reference it, you can't recall which workspace or which day you discussed it. Scrolling through sessions individually is impractical, and relying on memory to ask the model to recite it is unreliable. While dsh itself provides full-text session indexing and a cross-session reference injection mechanism, neither capability had a direct user interface previously. dsh-session-workbench fills this gap: it connects the three steps of search, location, and recall into a single interface, along with management of the session view tab bar. The following sections introduce the features, installation, and usage in detail. # What is dsh-session-workbench