Upgrade WebTorrent from v1.x to v2.8.5 (getBlob callback → blob() promise).
Patch the ESM bundle to expose window.WebTorrent global for script tag usage.

Create a persistent torrent gadget (gadget_cribjs_torrent) declared in
index.html alongside the router and header. It holds a single WebTorrent
client that survives page navigations — seeding no longer stops when the
user leaves the export page.

Migrate all 4 pages that used WebTorrent directly (export, save_load,
import, landing) to use acquired methods from the torrent gadget instead.
This eliminates 3 duplicate copies of downloadTorrent() and ensures a
single shared client instance.

Add share link + copy button to the save_load page after torrent seeding.
Add torrent_download acquisition chain through add_application for the
landing gadget.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>