dsh-plugin-minimax-usage: View MiniMax Coding Plan quota in DSH sidebar in real time

# Introduction When using DeepSeek Harness (DSH) with the MiniMax Coding Plan, checking the remaining quota requires switching to the MiniMax platform dashboard: the reset time for the 5-hour window and the current weekly usage are not visible on the screen. Switching back and forth while coding is highly disruptive. DSH's philosophy is "everything is a plugin," and the client UI is no exception. The `dsh-plugin-minimax-usage` introduced below is a client-side plugin: it renders the progress bars for the 5-hour and weekly quotas, along with reset countdowns, directly in the sidebar of the DSH web interface, refreshing every 60 seconds.