PERF.3 Apps: the "Save for offline" file list (128 KB inline, 2,054 files stat-ed per page, 42 ms) fetched on demand instead

Measured 2026-11-08: every app page carries <script id="cc-offline"> (128 KB: the URL of every file the service worker would save) and PHP spends 14 ms in AppBuilds::offlineFiles plus 28 ms in tools/shell/offline-size.php (a filesize of all 2,054 files) to build it. It is read only when a person clicks Save for offline (assets/js/app-offline.js) and by help-panel.js for the listed-files check.

Plan: keep key/page/bytes in the tag; move urls to a small endpoint (or a static JSON per release written by bin/release-app.php, a Discord member builds on demand) fetched when the button is pressed; cache offline_size per release (frozen) and per lab stamp for a Discord member. Saves about 15 KB gzipped per page view and 42 ms of PHP.