PERF.15 "Save for offline" downloads 107 to 260 MB per app; 103 MB of CadCraft's 173 MB is compiled help in 52 languages

Measured 2026-11-08 (bin/offline-size.php --libs): CadCraft 0.8.2 offline set 173 MB in 2,077 files: app files 161 MB, libraries 9.6 MB (pdfjs 5.2, three 2.1), shell 2.7 MB. Of the app files, help/ is 103 MB (52 compiled help.<locale>.js of 2 to 3 MB each plus 395 .md sources) and lang/ 33 MB (55 locale files); the modules a person runs are 3.7 MB at the top level. BimCraft 0.8.1 is similar; a Discord member builds reach 260 MB; MarkupCraft 78 MB carries 11.9 MB of Tesseract OCR data. On a phone this is a long download for one language.

Plan: the offline set keeps the chosen locale (its lang file and its help.<locale>.js) plus English, never all 52; help .md sources are not saved (the compiled help is what the panel reads); OCR language data per picked language; optional "all languages" switch for a shared classroom machine. AppBuilds::offlineFiles takes the locale (PERF.3 fetches the list on demand). Expected: CadCraft about 35 MB instead of 173 MB, with the same offline behaviour for that person. Test: bin/offline-size.php gains --locale and the service-worker test checks the saved copy opens the help in the picked language.