dsh-theme-rheostat: DSH "Rheostat" theme that shifts with model and inference levels

# Introduction DSH's philosophy is "everything is a plugin," and the theme is no exception. However, in daily use, if you switch between deepseek-v4-flash and deepseek-v4-pro or adjust the reasoning level, the interface lacks visual feedback corresponding to the specific setting, making different sessions appear identical. dsh-theme-rheostat, written by nineandnine-9, solves this issue: it maps the current session's model and reasoning level to four distinct visual "gears," ensuring the accent color, glow effects, and the indicator bar above the input box change accordingly. Unlike common static themes, its appearance is not a hardcoded color scheme but is driven by session state; in terms of implementation, it aligns with the maid-atelier theme referenced in the README.