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.

pnpm-lock.yaml

@@ -364,6 +364,9 @@ importers:
       '@vitejs/plugin-react':
         specifier: ^4.0.0
         version: 4.7.0(vite@6.4.3(@types/node@22.20.0)(jiti@2.7.0)(lightningcss@1.32.0)(tsx@4.22.4)(yaml@2.9.0))
+      fflate:
+        specifier: ^0.8.2
+        version: 0.8.3
       playwright:
         specifier: ^1.49.0
         version: 1.61.1