test(web): assembled session-log download e2e and refreshed golden

The navigation-panes replay scenario clicks the trajectory toolbar export
button and asserts the real host-streamed download: filename, a single
session.jsonl entry, and byte-verbatim seed content. The toolbar golden
refreshes for the localized export button.

apps/web/tests/snapshots/navigation-panes/trajectory.expected.md

@@ -2,7 +2,7 @@
   - button "Use actual duration": Duration
   - button "Collapse turns": Turns
   - button "Collapse calls": Calls
-  - button "导出会话日志": 导出
+  - button "Export session log": Export
   - img
   - searchbox "Search trajectory"
 - region "Trajectory timeline":