dsh-chat-cost: DeepSeek Harness Chat Cost Tracking Plugin

`dsh-chat-cost` is a plugin for the DeepSeek Harness (DSH) Web UI, designed to address the lack of transparency in cost tracking during agent development. It provides real-time cost breakdowns, multi-provider pricing support, local JSONL cost logging, and budget planning tools. After installation, configure log writing and language options, and refresh the price catalog with `npm run prices`. The plugin displays costs by conversation tree hierarchy, but note potential discrepancies with platform billing and data loss that may result from session interruptions.