dsh-goodmemory: Add automatic cross-session memory to DeepSeek Harness

dsh-goodmemory is a plugin for DeepSeek Harness (DSH) that provides cross-session long-term memory. Maintained by hjqcan, it utilizes GoodMemory as its backend. The plugin aims to address the lack of stable memory between DSH sessions by automatically recalling relevant memories prior to the model step (injected as an identifiable user message) and writing back the valid dialogue text of users and assistants after a successful turn, while excluding tool calls, reasoning processes, and injected content. The plugin supports two operating modes: the default "managed" mode automatically launches the goodmemory-http-bridge sidecar and uses SQLite for data storage, while the "external" mode connects to an existing GoodMemory instance.