lyuwen/queue-steer-button

Backlog composer controls for DeepSeek Harness, overriding the running-session input: Enter queues into the next agent step (next-step delivery after the observation), ⌘/Ctrl+Enter steers (aborts the current thinking step, keeps the partial output, continues with the new request), and ⌘/Ctrl+Shift+Enter sends to the backlog (DSH's native whole-turn queue). Pending messages render in a queue strip above the composer and can be pulled back into the text box for free-form editing.