feat(session): refuse session logs a build cannot faithfully read

Old runtimes meeting a newer session format now fail loud instead of
misreading: version refusal names the direction (newer: upgrade the
harness; older: no upgrade path) and points at the raw JSONL log, and an
event type outside the generated known vocabulary refuses resume unless
its envelope carries the new ignorable: true marker (default: required,
so a forgotten marker over-refuses instead of silently resuming a gutted
session). gen-persistence-catalog now also emits
KNOWN_SESSION_EVENT_TYPES; SQLite stores the marker in a dedicated
column (SCHEMA_VERSION 15). The versioning design (monotonic integer,
n->n+1 upgrader chain, migrate-on-continue) is recorded in the
session-log-version-mechanism Agent Note.

docs/subsystems/persistence.zh.md

@@ -87,6 +87,10 @@ interface SessionHeader {
 }
 ```
 
+## 格式拒绝：本构建无法可靠读取的日志
+
+后端用 `SessionFormatUnsupportedError` 拒绝无法可靠解读的日志，它与 `SessionPersistenceCorruptionError` 区分，因为数据没有损坏。header 的 `version` 比 `SESSION_FORMAT_VERSION` 新时，消息说明方向（"由更新的 harness 写入，请升级 harness 后打开"）；比它旧时说明本构建没有升级路径。经过 legacy 形状归一化后，本构建生成词汇表（`KNOWN_SESSION_EVENT_TYPES`，由 `gen-persistence-catalog` 生成）之外的事件类型同样被拒绝，除非该事件的信封带 `ignorable: true`：静默跳过一个不认识的必需事件可能改变日志其余部分的解读方式。后端为每个会话保留独立文件时，消息附上原始日志路径，被拒绝的文本仍然可读。设计理由与推迟建设的升级器链见 [session-log 版本机制 Agent Note](../../.agents/notes/implemented/architecture/2026-08-10-session-log-version-mechanism.md)。
+
 ## `CreateSessionOptions`：seed 与元数据
 
 通过 store 创建 `Session` 时会接收 `seed`（初始回放或 fork 历史）与 `meta`（store 折叠进 `SessionHeader` 的存储层字段）。store 填充 `version`/`id` 并为 `createdAt` 提供默认值；调用方可以提供已校验的绝对 `cwd`、`parentSession` 谱系、`seedLength` 种子边界、可选的粗粒度 `origin`、`delegationDepth`、该 agent 所依据组装的 `agentPreset` 以及已有的 `createdAt`。`origin: 'subagent'` 让产品导航能够隐藏重复的 child 行；它不证明描述符有效，也不证明 child 可以恢复。
@@ -342,5 +346,5 @@ abstract listSnapshots(signal?: AbortSignal): Promise<SessionPersistenceSnapshot
 
 Types: [SessionEvent](session.md) · [SessionId](core.md)
 
-Source: [`packages/session/session-persistence/src/index.ts:72`](../../packages/session/session-persistence/src/index.ts)
+Source: [`packages/session/session-persistence/src/index.ts:73`](../../packages/session/session-persistence/src/index.ts)
 <!-- END GENERATED cordis-surface -->