dsh-composer-collapse: DeepSeek Harness Web Composer Height Management Plugin

`dsh-composer-collapse` is a client-side-only plugin designed to address content occlusion caused by input field height constraints in the DSH Web environment. It only tightens the maximum height of the input field while preserving content auto-sizing. The plugin offers three height modes—auto, always expanded, and always collapsed—and supports switching between them via a button or keyboard shortcuts. It requires Chromium 105 or later and uses local storage to persist state. All side effects must be registered in `ctx.effect`, with element targeting based on official `data-*` attributes.