dsh-tool-activator: On-Demand Loading of DeepSeek Harness Tool Contexts

The `dsh-tool-activator` plugin is designed to address the issue of an oversized initial context in DeepSeek Harness (DSH). It shifts the tool loading strategy from “exposing all tools” to “loading core tools by default and activating the remaining tools on demand.” It supports a streamlined initial context, dynamic activation, state persistence, and configurable approval policies and tool grouping. Through the `activate_tools` interface, the plugin enables the model to dynamically retrieve specific tools when needed, and it performed stably in testing on 2026-10-11.