feat(core): busy_ack_skip_prefixes to silence queued-acks for automated actions

[MingChaoSun]

Motivation

Messages arriving while the agent is busy get a "message queued" acknowledgment so the user knows they were received. That's the right default for humans typing — but for high-frequency automated card actions the ack is pure noise.

Concrete case from my deployment: multi-question survey cards whose buttons dispatch commands (each click already updates the card synchronously via the card callback, similar to what #1828 generalizes). A user answering 8 questions in quick succession while a turn is running gets 8 queued-ack chat messages they don't care about, and each one yanks the chat viewport to the bottom — actively harmful UX.

What this adds

An opt-in per-project list:

[[projects]]
busy_ack_skip_prefixes = ["【问卷】", "cmd:【问卷】"]

• Messages whose content starts with any listed prefix are still queued and drained exactly as before — only the acknowledgment reply is suppressed.
• Card buttons dispatch their command as cmd:<text>, so deployments using both paths list both prefixes (documented).
• Empty/unset (default) acks every message — zero behavior change for existing configs.

Implementation

• Engine.SetBusyAckSkipPrefixes + hasAnyPrefix helper guarding the single MsgMessageQueued reply in queueMessageForBusySession.
• Wired from project config at both engine construction sites in cmd/cc-connect/main.go.
• Config validation rejects empty entries.
• Bilingual docs in config.example.toml next to agent_session_idle_timeout_mins.
• Tests: prefix suppression (both forms), default acks-everything preserved, hasAnyPrefix edge cases. go test ./core/ ./config/ green.

中文说明

新增可选的项目级配置 busy_ack_skip_prefixes：agent 忙碌期间到达的消息若命中前缀（如高频问卷按钮派发的命令），照常入队和补发，只是不再回"已入队"回执——连点 8 题不再刷 8 条噪音回执、聊天窗口不再被拽底。默认不配置=每条都回执，零行为变化。