refactor agent pre-step inbox lifecycle

packages/client/connection/src/client/fixture.ts

@@ -413,7 +413,7 @@ function viewFor(event: SessionEvent, log: readonly SessionEvent[]): ToolEventVi
  * Fixture parallel of the plan unit's double-event fold: `command/run`
  * records named `plan` set the wanted target (`off` → false, else true);
  * `plan/mode` commits and clears it. `wanted` is exposed for the prompt
- * boundary (the fixture's agent/step parallel).
+ * boundary (the fixture's step/start parallel).
  */
 function foldPlan(log: readonly SessionEvent[]): { active: boolean; pending: boolean; wanted: boolean | null } {
   let active = false
@@ -1189,7 +1189,7 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
         nextTurn.set(id, turn + 1)
         setRunning(id, true)
         append(id, { type: 'turn/start', data: { turn } })
-        // Boundary flush parallel (the host's agent/step seam): an outstanding
+        // Boundary flush parallel (the host's step/start observer): an outstanding
         // /plan selection commits as plan/mode inside the opened turn.
         const plan = foldPlan(logOf(id))
         if (plan.wanted !== null && plan.wanted !== plan.active) {

packages/client/runtime/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/client/runtime/README.md
-README.md: a116a5e4ad3070f20e6d90490f2507c1e2369c37
-README.zh.md: f375811e6f1480d6636fe4eb77746b76d6414b1e
+README.md: 645398e5efb429a82f612f2e6540924afd46cfd4
+README.zh.md: 572fe07128294bedae05a967ea8eee23532e4feb

packages/client/runtime/README.md

@@ -18,7 +18,7 @@ SlotsService gives the renderer separate bare observables for `useSessions` and
 
 ## Pending queue projection
 
-`ConversationSnapshot.queue` is the Host's authoritative transient Queue snapshot; pending steering stays outside this projection. Each row carries its `InboxItemId`, complete editable text when every content block is text, and a flattened preview. `session/queue` replaces the whole projection; reconnect buffering retains only the latest snapshot, and neither durable turn events nor running-status changes guess that an item was claimed. `Session.updateQueue()` sends edit/remove operations without optimistic mutation, so the next Host snapshot is the sole visible commit and a claim race can surface `queue-item-not-found`.
+`ConversationSnapshot.queue` is the Host's authoritative transient snapshot of `agent.inbox.nextTurn`; pending next-step steering stays outside this projection. Each row carries its `MessageId`, complete editable text when every content block is text, and a flattened preview. The Host derives whole `session/queue` snapshots from durable `agent/inbox/spliced` mutations and sends a baseline on reconnect; the message-local `agent/inbox/inserted`, `claimed`, and `discarded` notifications are not used to reconstruct this projection. `Session.updateQueue()` sends edit/remove operations through Host-side `Inbox.splice()` without optimistic client mutation, so the next Host snapshot is the sole visible commit and a claim race can surface `queue-item-not-found`.
 
 ## Code Mode sub-dispatch index
 

packages/client/runtime/README.zh.md

@@ -18,7 +18,7 @@ SlotsService 分别为 renderer 提供 `useSessions` 与 `useWorkspaces` 的裸
 
 ## 待处理队列投影
 
-`ConversationSnapshot.queue` 是 Host 提供的权威瞬态 Queue 快照；待处理 steering（中途引导）不进入此投影。每行都携带其 `InboxItemId`、所有内容块均为文本时的完整可编辑文本，以及扁平化预览。`session/queue` 会整体替换该投影；重连缓冲只保留最新快照，持久轮次事件和 running 状态变化都不会猜测某个项已被认领。`Session.updateQueue()` 发送编辑／移除操作，不进行乐观更新，因此下一份 Host 快照是唯一可见的提交结果，认领竞态则会返回 `queue-item-not-found`。
+`ConversationSnapshot.queue` 是 Host 提供的 `agent.inbox.nextTurn` 权威瞬态快照；待处理的 next-step steering（中途引导）不进入此投影。每行携带其 `MessageId`、所有内容块均为文本时的完整可编辑文本，以及扁平化预览。Host 根据持久 `agent/inbox/spliced` 变更派生完整 `session/queue` 快照，并在重连时发送基线；面向单条消息的 `agent/inbox/inserted`、`claimed` 与 `discarded` 通知不用于重建该投影。`Session.updateQueue()` 经 Host 侧 `Inbox.splice()` 发送编辑／移除操作，客户端不做乐观变更，因此下一份 Host 快照是唯一可见的提交结果，claim 竞态则会返回 `queue-item-not-found`。
 
 ## Code Mode 子调用索引