dsh-session-index: A DSH full-text indexing plugin enabling agents to retrieve historical sessions

# Introduction When developing agents with DSH, you will quickly encounter a specific problem: sessions are isolated from one another. When starting a new dialogue, the agent cannot retrieve what was said previously or which tools were invoked. Attempting to write a plugin to subscribe to `session/event` to accumulate logs is also insufficient—`session/event` is an "append-only" event stream, and resumed sessions do not replay the seed historical events, making it impossible to access the content of old sessions. `dsh-session-index` fills this gap: it builds a cross-session full-text index of all session content and exposes it as a tool that the model can call directly. Below is an introduction to its positioning, working mechanism, and installation steps. # What is `dsh-session-index`?