dsh-dictate: Integrate voice input into DSH Composer

dsh-dictate is a context-aware voice input plugin designed for DeepSeek Harness (DSH) Composer. It facilitates voice input for long prompts or code explanations, preserving transcriptions in the input box for user review and modification, and does not initiate a bidirectional voice session. By default, the plugin uses the Web Speech API in Chrome or Edge for browser-based recognition, displaying real-time transcriptions during recording. On Apple Silicon Mac and Windows x64 platforms, users can choose to employ the local SenseVoice model for enhanced transcription, requiring the download of approximately 253 MB of model files. Its core advantages include context-awareness (optimizing wording based on the last 6 conversations), optimized recognition for Chinese-English mixed text, and strict send controls (defaulting to no automatic sending).