fix(agent-loop): park empty turn batches, keep max-tokens sticky, and settle headless at idle

- turn boundary now returns false for an empty admitted batch (claimed
  input removed before the wake) instead of opening a turn and spending a
  model call on nothing; the step boundary already had the symmetric guard.
- a max-token step stays sticky when steering or injected work continues
  the turn: a later completed step no longer downgrades the outcome,
  matching the TurnEndReasonMap contract.
- session/queue wire schema accepts the context placement (previously the
  zod union rejected injected-context snapshots wholesale and the client
  silently dropped the whole frame); schema tests cover all placements.
- headless runs settle at whole-agent idle instead of the first turn/end,
  honoring the one-shot idle-to-idle contract.
- flush JSDoc names the real callers (checkpoint policy, goal-session,
  teardown, self-flushing consumers); apiproxy zh README loses its stale
  duplicate history section; ACP note/README record the delivered error
  rejection and turnless-cancelled behaviors.

packages/acp/acp/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/acp/acp/README.md
-README.md: 4632c00398d0870d3682d8c6241e26de006ad233
-README.zh.md: 1bfd16def64f7973ae4e517dfc96e32478b49aa2
+README.md: a48224fca8aac12e1440e187cfc4b418952d0951
+README.zh.md: 953b7791a0948620706d86a5c30f6629bdd11ae4

packages/acp/acp/README.md

@@ -24,7 +24,7 @@ Both fields are optional so another agent/request listener may supply the target
 | `initialize` | Negotiates the supported version and advertises baseline-only prompts (no image, audio, or embedded-context capability). No session, editor, terminal, filesystem, or MCP capability is advertised. |
 | `authenticate` | No-op because the server advertises no authentication methods. |
 | `session/new` | Creates a fresh agent with an absolute primary `cwd`; empty `additionalDirectories` and `mcpServers` are accepted, non-empty values reject. |
-| `session/prompt` | Concatenates text blocks, renders baseline resource links as bracketed textual references, rejects empty or beyond-baseline input, permits one in-flight request per session, and waits for the whole agent to become idle. Normal quiescence reports `end_turn`; explicit ACP cancellation or disposal reports `cancelled`. |
+| `session/prompt` | Concatenates text blocks, renders baseline resource links as bracketed textual references, rejects empty or beyond-baseline input, permits one in-flight request per session, and waits for the whole agent to become idle. Normal quiescence reports `end_turn`; explicit ACP cancellation, disposal, or a prompt whose admission was discarded (a turnless slot) reports `cancelled`. |
 | `session/cancel` | Cancels only the addressed agent and settles its pending prompt as `cancelled`; unknown ids are no-ops. |
 | `session/update` | Emits one `agent_message_chunk` per non-empty text block in a committed `assistant/message`. Raw deltas and non-message events are omitted. |
 | `session/request_permission` | Offers one-shot allow/reject choices for bridge-owned approval requests carrying a tool call id. Clients may answer automatically. |
@@ -37,7 +37,7 @@ Committed-message output intentionally trades token-by-token latency for a clean
 
 Client disconnect and Cordis disposal share one memoized teardown. The bridge first rejects new sessions and prompts, settles pending prompts, then drains continuable descendants only below this connection's exact owned Agents before disposing those handles in parallel and awaiting every result before reporting any failure. Other frontends sharing the Context retain their continuable forests and admission. An ACP-only plugin reload therefore leaves no orphan agent.
 
-ACP requires each prompt response to carry a `stopReason`, but the bridge does not claim a prompt-specific turn outcome. Committed assistant messages stream across the owned activity, and steering or injected work may contribute before idle. Token-limit and model-error turn endings therefore do not become prompt-level ACP stop reasons.
+ACP requires each prompt response to carry a `stopReason`, but the bridge does not claim a prompt-specific turn outcome. Committed assistant messages stream across the owned activity, and steering or injected work may contribute before idle. Token-limit turn endings therefore do not become prompt-level ACP stop reasons (they settle as `end_turn`); a model error on the correlated turn rejects the prompt immediately.
 
 ## Running
 

packages/acp/acp/README.zh.md

@@ -24,7 +24,7 @@
 | `initialize` | 协商受支持的版本，并仅公布基线提示词（无图像、音频或嵌入上下文能力）。不公布会话、编辑器、终端、文件系统或 MCP 能力。 |
 | `authenticate` | 空操作，因为服务器不公布身份验证方法。 |
 | `session/new` | 以绝对路径作为主 `cwd` 创建新 agent；接受空的 `additionalDirectories` 和 `mcpServers`，拒绝非空值。 |
-| `session/prompt` | 拼接文本块，将基线资源链接渲染为带方括号的文本引用，拒绝空输入或超出基线的输入，每个会话只允许一个正在处理的请求，并等待整个 agent 进入 idle。正常完全停稳时报告 `end_turn`；显式 ACP 取消或资源释放时报告 `cancelled`。 |
+| `session/prompt` | 拼接文本块，将基线资源链接渲染为带方括号的文本引用，拒绝空输入或超出基线的输入，每个会话只允许一个正在处理的请求，并等待整个 agent 进入 idle。正常完全停稳时报告 `end_turn`；显式 ACP 取消、资源释放，或准入被丢弃的提示词（turnless 槽位）时报告 `cancelled`。 |
 | `session/cancel` | 仅取消指定的 agent，并将其待处理提示词结算为 `cancelled`；未知 id 为空操作。 |
 | `session/update` | 为每个非空文本块发出一个 `agent_message_chunk`；这些文本块来自已提交的 `assistant/message`。省略原始增量和非消息事件。 |
 | `session/request_permission` | 为携带工具调用 id、由桥接层拥有的批准请求提供一次性允许／拒绝选项。客户端可以自动回答。 |
@@ -37,7 +37,7 @@
 
 客户端断开与 Cordis 释放共用同一个记忆化清理流程。桥接层先拒绝新会话和提示词，结算待处理提示词，然后只 drain 此连接确切拥有的 Agent 之下的可继续后代，再并行释放这些 handle，并等待全部结果结算后才报告失败。其他共享该上下文的前端会保留其可继续森林和准入。因此，仅 ACP 的插件重载不会遗留 agent。
 
-ACP 要求每个提示词响应都携带 `stopReason`，但桥接层不声称它表示提示词专属的轮次结果。已提交的 assistant 消息会在整个自有活动期间流式输出，agent 进入 idle 前发生的 steering（中途引导）或注入工作也可能参与其中。因此，因 token 上限或模型错误而结束的轮次不会成为提示词级 ACP 停止原因。
+ACP 要求每个提示词响应都携带 `stopReason`，但桥接层不声称它表示提示词专属的轮次结果。已提交的 assistant 消息会在整个自有活动期间流式输出，agent 进入 idle 前发生的 steering（中途引导）或注入工作也可能参与其中。因此，因 token 上限而结束的轮次不会成为提示词级 ACP 停止原因（它们以 `end_turn` 结算）；关联轮次上的模型错误会立即 reject 提示词。
 
 ## 运行