dsh-as-aistudio: Google AI Studio-style Turn Control for DeepSeek Harness

The `dsh-as-aistudio` plugin for DeepSeek Harness (DSH) aims to address the lack of fine-grained control over individual conversation turns when debugging agents. It integrates editing, rerunning, deletion, and Markdown preview capabilities into DSH, with each feature operating independently and without interfering with the others, similar to the Google AI Studio environment. Users can install the plugin with a single command and then hover over messages in the chat interface to edit and rerun, rerun, or delete responses. The plugin also provides state visualization and displays component status in the settings. Installation requires DSH version >= 0.1.6-alpha.2, and after modifying the source code, a rebuild and host restart are required.