按规划继续工作

结论：补齐通用会话快照 envelope 的格式、版本、会话 ID 与对象形状拒绝验证，覆盖 Node OPFS 与 Chromium OPFS 路径，并通过 host/WASM/browser 聚合验证。

wasm-port/docs/source-reuse-map.md

@@ -83,7 +83,8 @@ Current validation is intentionally mechanical:
   `runtime/opfs/file-service.js` adapter. `runtime/opfs/path-model.js` now
   defines paths for INI, tool table, parameter file, G-code program,
   preview-cache, and session-snapshot targets. `runtime/opfs/snapshot-store.js`
-  adds a generic JSON session snapshot envelope.
+  adds a generic JSON session snapshot envelope and validates its format,
+  version, session id, metadata, and payload shape.
   `runtime/opfs/machine-file-store.js` adds pure-text storage for INI, tool
   table, parameter file, and G-code program content.
   `runtime/opfs/linuxcnc-parameter-bridge.js` copies OPFS-backed parameter