dsh-composer-history: Provides arrow key command history for DSH Web GUI composer

`dsh-composer-history` is a plugin for the DSH Web GUI composer, designed to address the lack of a command history review feature in the input box. Rather than altering the message sending logic, this plugin extends the input box behavior, enabling users to browse previously sent commands using `↑ / ↓` arrow keys. Its core functionality includes pressing `↑` to switch to older commands and pressing `↓` to switch to newer commands; pressing `↓` again after reaching the latest entry restores the draft prior to editing. The plugin only tracks completed user messages and does not trigger on multi-line input, IME composition, or specific modifier key presses, thereby avoiding interference with normal input. Installation can be performed using `dsh plugin --profile web add github:baisama-cloud/dsh-c`