fix(session): refuse foreign format versions before parsing current structure

Review round: the JSONL backend now refuses a foreign header version straight
from the raw header line, before validating today's header shape or decoding
any event row, so a structurally different future format reports the upgrade
direction instead of corruption (shared message builder
sessionFormatVersionRefusal). HMR live-prefix adoption runs the unknown-type
guard like the other read paths. The appendCore comment now states why the
unknown-type guard is read-side only, the loadStoredFrom JSDoc and README pin
the seek-vs-sequential refusal-scope divergence, and the generated catalog
preamble lists the ignorable envelope field.

docs/subsystems/persistence.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 docs/subsystems/persistence.md
-persistence.md: de7c5c4d445986fe306a782683a8559b25677c94
-persistence.zh.md: a52506aa86418f66e6b1a372020cc316f67cc1c7
+persistence.md: 7deaa9b30b5a6b1e3cbdcc38255b3974b5abf477
+persistence.zh.md: c5afcf67319da408b739d41b2b7ad3eb434ffbad

docs/subsystems/persistence.md

@@ -89,7 +89,7 @@ interface SessionHeader {
 
 ## Format refusal — logs a build cannot faithfully read
 
-A backend refuses a log it cannot faithfully interpret with `SessionFormatUnsupportedError`, distinct from `SessionPersistenceCorruptionError` because nothing is damaged. A header `version` ahead of `SESSION_FORMAT_VERSION` names the direction ("written by a newer harness — upgrade the harness to open it"); one behind it states that this build ships no upgrade path. After legacy-shape normalization, an event type outside this build's generated vocabulary (`KNOWN_SESSION_EVENT_TYPES`, emitted by `gen-persistence-catalog`) refuses the same way unless the event's envelope carries `ignorable: true` — silently skipping an unrecognized required event could change how the rest of the log must be read. The message appends the raw log path when the backend keeps one artifact per session, so the refused text stays reachable. Design rationale and the deferred upgrader chain live in the [session-log-version-mechanism note](../../.agents/notes/implemented/architecture/2026-08-10-session-log-version-mechanism.md).
+A backend refuses a log it cannot faithfully interpret with `SessionFormatUnsupportedError`, distinct from `SessionPersistenceCorruptionError` because nothing is damaged. A header `version` ahead of `SESSION_FORMAT_VERSION` names the direction ("written by a newer harness — upgrade the harness to open it"); one behind it states that this build ships no upgrade path. After legacy-shape normalization, an event type outside this build's generated vocabulary (`KNOWN_SESSION_EVENT_TYPES`, emitted by `gen-persistence-catalog`) refuses the same way unless the event's envelope carries `ignorable: true` — silently skipping an unrecognized required event could change how the rest of the log must be read. The message appends the raw log path when the backend keeps one artifact per session, so the refused text stays reachable. The JSONL backend refuses a foreign version straight from the raw header line, before validating today's header shape or decoding any event row — a structurally different future format still reports the upgrade direction, never "corrupt"; SQLite gates whole-file structure through its own `SCHEMA_VERSION` pragma first. Design rationale and the deferred upgrader chain live in the [session-log-version-mechanism note](../../.agents/notes/implemented/architecture/2026-08-10-session-log-version-mechanism.md).
 
 ## `CreateSessionOptions` — seeding and metadata
 
@@ -346,5 +346,5 @@ abstract listSnapshots(signal?: AbortSignal): Promise<SessionPersistenceSnapshot
 
 Types: [SessionEvent](session.md) · [SessionId](core.md)
 
-Source: [`packages/session/session-persistence/src/index.ts:73`](../../packages/session/session-persistence/src/index.ts)
+Source: [`packages/session/session-persistence/src/index.ts:74`](../../packages/session/session-persistence/src/index.ts)
 <!-- END GENERATED cordis-surface -->

docs/subsystems/persistence.zh.md

@@ -89,7 +89,7 @@ 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)。
+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。JSONL 后端直接从原始 header 行拒绝外来版本，先于当前 header 形状校验和任何事件行解码，因此结构完全不同的未来格式仍会报告升级方向，绝不会报"损坏"；SQLite 则先由自己的 `SCHEMA_VERSION` pragma 把关整个文件的结构。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
 
@@ -346,5 +346,5 @@ abstract listSnapshots(signal?: AbortSignal): Promise<SessionPersistenceSnapshot
 
 Types: [SessionEvent](session.md) · [SessionId](core.md)
 
-Source: [`packages/session/session-persistence/src/index.ts:73`](../../packages/session/session-persistence/src/index.ts)
+Source: [`packages/session/session-persistence/src/index.ts:74`](../../packages/session/session-persistence/src/index.ts)
 <!-- END GENERATED cordis-surface -->