Description

EN: When the Agent mode executes a multi-step todo list created in Plan mode, user messages typed mid-turn (pressing Enter) are enqueued into queued_messages but only consumed at TurnComplete — i.e. after all todos have finished. There is no mid-turn intervention path between "wait for everything" (Enter → Queue → TurnComplete) and "nuke the entire turn" (Esc).

CN: Agent 模式执行 Plan 模式梳理的多步 todo 时，用户中途按 Enter 的消息会进入 queued_messages，但只在 Turn 完成（全部 todos 执行完毕）后才被消费。用户缺少"等全部"和"炸掉整个 Turn"之间的中间粒度干预手段。

Steps to reproduce

1. EN: In Plan mode, have the assistant produce a checklist_write with 5 todos.
   CN: Plan 模式下让助手生成一个 5 步的 checklist_write。
2. EN: Switch to Agent mode, send a message to trigger full-plan execution.
   CN: 切到 Agent 模式，发一条消息触发全量执行。
3. EN: While the assistant is executing todo #2, type "skip todo #4, do X instead" in the composer and press Enter.
   CN: 助手执行到第 2 步时，在输入框输入 "跳过 todo #4，改为方案 X" 并按 Enter。
4. EN: Observe: the message appears in the Pending inputs preview area but is not acted on.
   CN: 观察：消息出现在 Pending inputs 预览区，但不会立即生效。
5. EN: Wait — the assistant finishes #3, #4, #5 as originally planned. Only then does the queued message dispatch as a new turn.
   CN: 等待 —— 助手按原计划执行完 #3、#4、#5，Turn 结束后排队消息才被 dispatch。

Expected behavior

EN: A mid-turn intervention mechanism with finer granularity than "Esc the whole turn":

• Ability to promote a selected queued message into an immediate steer, or
• A "send now" action in the PendingInputPreview widget that steers the chosen item into the current turn.

CN: 一个比"Esc 整个 Turn"更细粒度的干预通道：

• 能将选中的排队消息提升为即时 steer 注入当前 Turn，或
• PendingInputPreview 中提供逐条"立即发送"的快捷操作。

Actual behavior

EN: decide_submit_disposition() returns Queue uniformly when is_loading = true. The main Turn loop in the engine drains rx_steer (used by Ctrl+Enter) every iteration, but never inspects queued_messages. At TurnComplete, only one message is popped via pop_queued_message() — the rest wait for subsequent turns, which themselves re-enter loading state, perpetuating the backlog.

Key code sites:

• crates/tui/src/tui/app.rs:3504-3512 — decide_submit_disposition
• crates/tui/src/tui/ui.rs:1024-1025 — end-of-turn consumption (single pop)
• crates/tui/src/tui/ui.rs:2291 — Tab also queues, does not steer
• crates/tui/src/core/engine/turn_loop.rs:50 — steer channel drained per step, but only via Ctrl+Enter

CN: decide_submit_disposition() 在 is_loading = true 时统一返回 Queue。Engine 层的 Turn 循环每轮都会 drain rx_steer（Ctrl+Enter 专用通道），但从不会检查 queued_messages。TurnComplete 后只 pop_queued_message() 一条，其余继续等待后续 Turn，而这些新 Turn 又会进入 loading 状态，形成排队积压。

关键代码锚点：

• crates/tui/src/tui/app.rs:3504-3512 — decide_submit_disposition
• crates/tui/src/tui/ui.rs:1024-1025 — TurnComplete 后只弹一条
• crates/tui/src/tui/ui.rs:2291 — Tab 也是 queue，非 steer
• crates/tui/src/core/engine/turn_loop.rs:50 — steer 通道只在 Ctrl+Enter 时被写入

Environment

• OS: Linux
• DeepSeek CLI version: 0.8.x (current main)
• Model: deepseek-v4-pro / deepseek-v4-flash
• Shell: bash