dsh-client-ui-quickfill: Terminal-Style Prompt History and Quick Completion

The `dsh-client-ui-quickfill` plugin introduces a shell-like editing experience to DSH Web Composer, supporting multi-line/single-line history navigation, fuzzy search (Ctrl+R), and Fish-style auto-completion. It preserves the current draft state and supports cross-session history storage (disabled by default), with all data kept local. It requires installation in a pnpm environment and a service restart. Note potential conflicts with macOS Cmd+R and font compatibility.