fix(session-export): flush live logs before raw reads

The exporter read persistence artifacts directly even when the requested root or a descendant was still live. Buffered session events could therefore be omitted from a successful download, so the advertised verbatim-artifact guarantee described storage accurately but captured an arbitrarily stale durability boundary.

Resolve each id against SessionStore and cross its authoritative flush barrier immediately before readRaw. Cold sessions remain a no-op, while live roots and descendants are made durable independently; this intentionally yields a per-session read-boundary snapshot rather than claiming an atomic lineage snapshot. A host-path regression test proves both artifacts change from stale to durable only through flush, and the bilingual host contract and Agent Note document the boundary.

.agents/notes/implemented/feature/2026-08-10-web-session-log-export.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 .agents/notes/implemented/feature/2026-08-10-web-session-log-export.md
-2026-08-10-web-session-log-export.md: 838fbc77c82e8472ccf419e2d55e0396212fd1ba
-2026-08-10-web-session-log-export.zh.md: 5d9b168ea99f02211aafc794a36f8c7d2bb002a8
+2026-08-10-web-session-log-export.md: a290eb7043833b66a217476a86c985ec8c9f33de
+2026-08-10-web-session-log-export.zh.md: b02fff598048250fe747f124ad86cd98352aa28f

.agents/notes/implemented/feature/2026-08-10-web-session-log-export.md

@@ -24,7 +24,7 @@ The Trajectory view had no way to hand a debugging artifact to a human: the raw
 
 ## Consequences
 
-- Export fidelity: every exported file is byte-identical to the backend's durable artifact as of the read moment (a live session may append after the read; the export reflects the durable state at read time). The archive name is `dsh-session-<sanitized-id>.zip` and archive paths sanitize ids before they can shape entries.
+- Export fidelity: immediately before reading each live root or descendant, the exporter crosses the authoritative `SessionStore.flush` durability barrier; every exported file is byte-identical to that resulting durable artifact. A live session may append again after its read, so the archive is a per-session read-boundary snapshot rather than one atomic tree snapshot. The archive name is `dsh-session-<sanitized-id>.zip` and archive paths sanitize ids before they can shape entries.
 - `supportsRawArtifacts` explicitly separates backend capability from session absence: unsupported backends such as SQLite report `false` and the concrete `readRaw` default rejects, while the JSONL override reports `true`, owns physical decoding, and reserves `undefined` for an absent artifact. `ApiProxy.downloads.sessionLog` adds one host-only member to the contract plus a host-side query schema and a GET branch in the fetch handler — no RPC map row, envelope schema, or client `IApiClient` surface.
 - Fixture mode (no host) answers 404 for the export, which the browser reports as a failed download; the navigation-panes golden snapshot includes the 导出 button.
 - Deferred: transcript.md and a report/feedback bundle remain future work; the byte-faithful, manifest-free shape keeps the v2 bundle extension cheap.

.agents/notes/implemented/feature/2026-08-10-web-session-log-export.zh.md

@@ -24,7 +24,7 @@ Trajectory 视图没有任何方式把调试工件交到人手里：原始会话
 
 ## 后果
 
-- 导出保真度：每个导出文件都与读取时刻的后端持久化工件逐字节一致（活跃会话可能在读取后继续追加；导出反映的是读取时的持久化状态）。压缩包名为 `dsh-session-<sanitized-id>.zip`，归档路径在塑造条目前会先净化会话 id。
+- 导出保真度：读取每个实时根会话或后代前，导出器会通过权威的 `SessionStore.flush` 持久性屏障；每个导出文件都与由此得到的持久化工件逐字节一致。实时会话可能在自身读取后再次追加，因此归档是按会话读取边界形成的快照，而不是整棵树的原子快照。压缩包名为 `dsh-session-<sanitized-id>.zip`，归档路径在塑造条目前会先净化会话 id。
 - `supportsRawArtifacts` 明确区分后端能力与会话缺失：SQLite 等不支持的后端报告 `false`，具体 `readRaw` 默认会拒绝；JSONL 覆写则报告 `true`、自持物理解码，并只用 `undefined` 表示工件缺失。`ApiProxy.downloads.sessionLog` 为契约新增一个 host-only 成员，外加宿主侧 query schema，并在 fetch handler 加一个 GET 分支——没有 RPC map 行、信封 schema 或客户端 `IApiClient` 面。
 - fixture 模式（无宿主）对导出应答 404，浏览器会将其报告为下载失败；navigation-panes golden 快照包含「导出」按钮。
 - 暂缓：transcript.md 以及 report/feedback 打包留待后续；逐字节忠实、无清单的形态让 v2 的打包扩展保持廉价。