dsh-turn-cost-pill: Display "Previous round cost" next to the input box

The DSH plugin `dsh-turn-cost-pill` (maintainer: ly13277, repository: DshRmbCostPer1Talk) displays the RMB cost of the latest interaction in the current session to the right of the "Permission" button in the input box. When a round is completed, it shows "Last ¥0.0123"; if the current round is ongoing, it shows "Current ¥0.0041" with a small green dot, and the amount increases in real-time with each request step. Hovering reveals uncached input, cache hits, output tokens, and the model used. Data is sourced from usage reported by the provider for each billing request in the session logs, aggregated by "round + step". Retries are also counted. The Host side only registers the session projection; it does not initiate model requests, collect, or upload data. Costs are calculated based on DeepSeek's official peak/off-peak rates: Flash cache hit 0.02, cache miss input 1, output 4; Pro 0.15/4.5/13.5; with a multiplier of 2 during peak hours. Non-DeepSeek models fall back to Flash prices and are marked with an approximate equals sign. Install using `dsh plugin --profile web add github:ly13277/DshRmbCostPer1Talk`, and uninstall using `remove dsh-turn-cost-pill`. The amounts are estimates rather than the original bill values; steps without usage reports will not be displayed.