fix(persistence): restore pre-identity sessions

packages/core/session/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/core/session/README.md
-README.md: 40516d12180de9c30efd40fdffa873da20ddacb3
-README.zh.md: 43842643a3434c741f219f7b6c26622cddfae8e7
+README.md: a9b6905dcf2b8ef1f75595e567273f7a3150a412
+README.zh.md: f1a5e97e32d1ad1abcd6ad96e6c621af9972e989

packages/core/session/README.md

@@ -142,5 +142,5 @@ Logging causes no invalidation, and exact reconstruction preserves request-prefi
 
 - **Session branching/tree** (pi-style entry tree) — deferred unless needed beyond boundary-based `fork()`.
 - **`fork()` cuts only at stable boundaries of live sessions** — the selected prefix must end outside an open turn and the source must be in the store; forking a persisted-but-unloaded session is excluded from the [fork API](../../../.agents/notes/implemented/feature/2026-06-30-session-store-fork-api.md).
-- **`SESSION_FORMAT_VERSION` stays pinned at `0`** — pre-release, no compatibility implied: a backend rejects any other version, and no migration path exists until the first release ([policy](../../../AGENTS.md)).
+- **`SESSION_FORMAT_VERSION` stays pinned at `0`** — pre-release, no broad compatibility implied: `Session` accepts only current seed shapes and a backend rejects any other version. Narrow storage import upgrades belong to the persistence boundary ([policy](../../../AGENTS.md), [pre-identity message recovery](../../../.agents/notes/implemented/bug-fix/2026-07-28-load-pre-identity-session-messages.md)).
 - **`TurnEndReasonMap` omits the ACP-named `refusal` / `max_turn_requests` variants** — producer-gated: they land when an adapter or the loop first emits them.

packages/core/session/README.zh.md

@@ -142,5 +142,5 @@
 
 - **会话分支／树**（pi 风格条目树）：除非需要超越基于边界的 `fork()` 能力，否则暂缓。
 - **`fork()` 仅在实时会话的稳定边界处切分**：所选前缀结束时不得有开放轮次，且源会话必须位于存储中；[fork API](../../../.agents/notes/implemented/feature/2026-06-30-session-store-fork-api.md) 不支持对已持久化但未加载的会话进行 fork。
-- **`SESSION_FORMAT_VERSION` 固定为 `0`**：预发布阶段不承诺兼容性；后端会拒绝其他任何版本，首次发布前不提供迁移路径（[政策](../../../AGENTS.md)）。
+- **`SESSION_FORMAT_VERSION` 固定为 `0`**：预发布阶段不承诺广泛兼容性；`Session` 只接受当前 seed 形状，后端会拒绝其他任何版本。范围受限的存储导入升级应由持久化边界负责（[政策](../../../AGENTS.md)、[消息标识机制引入前的消息恢复](../../../.agents/notes/implemented/bug-fix/2026-07-28-load-pre-identity-session-messages.md)）。
 - **`TurnEndReasonMap` 不含 ACP（Agent Client Protocol）命名的 `refusal`／`max_turn_requests` 变体**：受生产方约束；只有当适配器或循环首次产生这些变体时才加入。