Prompt queue — type follow-ups while a turn is running

[aakashrajput]

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Why

During a long agentic turn the input box is idle — users think of the next instruction and have nowhere to put it. Queued prompts keep flow.

What

Prompt queue:

• Typing + Enter while a turn is running enqueues the message instead of rejecting it; queued items render as small chips above the input (with a count)
• When the turn completes, queued prompts submit in order automatically
• Up/down to review queue, delete key to remove an item, Esc clears focus back to normal
• Queue survives within the session only (no persistence needed for v1)

Where to start

• Input handling + turn state: src/screens/repl.ts (the busy/streaming flag already exists), input widget in src/engine/
• Paste chips are a similar existing UI pattern to copy

Acceptance criteria

• Queue 2 messages mid-turn → they run sequentially after the turn ends, each as its own turn
• Ctrl+C during a queued run cancels cleanly without losing the remaining queue
• typecheck green