from_preset() set userAgent, platform and oscpu from the captured device
but never appVersion. Firefox reports appVersion as "5.0 (<OS tokens>)",
so leaving it unset let the host's own value through — and a page reading
two properties saw them disagree.
Measured on 152.0.4-beta.29, macOS host, os="linux", fingerprint_preset:
navigator.platform Linux x86_64
navigator.appVersion 5.0 (Macintosh) <- the host
The value is derived from the user agent rather than from the platform,
because 20 of the 65 bundled Linux presets carry a distro token
("X11; Ubuntu") that a platform lookup would flatten to "X11" — a smaller
mismatch than the host leaking, but the same kind. Firefox builds
appVersion from the same OS tokens as the UA, minus the architecture and
the Gecko revision, with Windows collapsed to its family name; checked
against 800 browserforge fingerprints, the derivation is exact on every
one, including Android and the Ubuntu variant.
A preset that ships its own appVersion keeps it, and a user agent the
rule cannot parse leaves the key unset rather than inventing a value.
(cherry picked from commit 759e4ab2fa)
