feat(codex): surface non-blocking asks from request_user_input_async

[Tryanks]

What changes

Codex's app-server (checked against codex-cli 0.156.1) exposes request_user_input_async to models whose catalog advertises it. This is the non-blocking ask in the Codex desktop app. It is not a server request. The tool completes an agentMessage item with questions: [{title, options?}] and delivery: "async", and the turn keeps running. The desktop app and the TUI answer with ordinary user input wrapped in <send_user_message_question_reply>[{answer, question, questionItemId}]</send_user_message_question_reply>. The questionItemId is JSON.stringify(["request_user_input_async", itemId, index]).

Tcode now surfaces it natively:

• Contract. AgentEvent::UserInputRequested gains delivery: UserInputDelivery (Blocking or Async). It defaults to Blocking and is omitted when blocking, so persisted logs and the other providers are unchanged.
• Codex client. A completed agentMessage with questions becomes an Async request. The item itself is recorded as a request_user_input_async tool call, not assistant text, because its text only repeats the questions the panel shows. Tool rows summarize question tools by their first question. Open questions of a turn accumulate under the latest message id, so a second ask does not hide an unanswered first one. RespondUserInput sends a turn/steer carrying Codex's envelope. It emits SteerRequested with the TUI's plain > question / answer rendering, and the existing userMessage echo matching emits SteerAccepted. turn/completed discards unanswered questions, as the TUI does.
• Timeline. The pending request is now a PendingUserInput struct with the delivery, replacing the tuple.
• Composer. While an async question is open, Enter, steering and digit keys behave as usual. The panel shows a header in place of the missing one, a hint that the agent keeps working, and a close button that hides it on this client until a newer request arrives. New strings are added in English and Chinese.

Tests

• async_question_answers_steer_the_running_turn_with_codex_reply_envelope uses the recorded item shape. It asserts the tool-call item, the question ids, the literal turn/steer envelope, steer acceptance on the echo, and rejection once the turn has ended.
• user_input_delivery_is_async_only_when_recorded asserts that a legacy persisted event decodes as blocking and checks the literal async encoding.

Checks run

• cargo fmt --all --check, cargo clippy --workspace --all-targets --locked -- -D warnings, cargo nextest run --workspace --locked: all pass locally on macOS (941 tests).
• Live probe against codex-cli 0.156.1 on gpt-6-astra: the model asked, kept running, received the steered answer and replied with it.
• Desktop app on a throwaway profile, light theme at wide width and dark theme at narrow width: the panel appears while sleep runs, answering closes it and steers, and the close button hides it without stopping the turn.
• Not run locally: the iOS, Android, Web and machete CI jobs.