Until #809 a display:none rule in mobile.css and its KNOWN_PHONE_HIDDEN
entry kept the File Viewer button off phones, and the gate checked both.
With that rule gone, the handheld default in getDefaultSettings() and the
html.mobile-init startup rule are the whole lock, and only the browser
test saw them, which npm test does not run.
The policy test now loads the real getDefaultSettings() on a handheld and
on a desktop, checks that every reader of the setting goes through the
device default, and that mobile.css keeps the startup hide.
Docs: architecture-invariants, src/web/CLAUDE.md and the wiki say the
button is off on a phone until it is switched on there, and that a window
narrower than 600px on a device that is not a handheld now shows it.
Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>
Codeman maintainer
d192eb6825