keyUsesUserScope returned true for any key the registry did not know, so a
client could invent a production setting unilaterally and the server stored
it as an unvalidated string. That is how six ui.* settings and five orphan
keys reached production untyped, and it is the root enabler the design
names.
An unknown key is no longer a user setting, so the legacy write path
rejects it and the canonical API — which validates every value against its
own definition — is the only way to store something new.
jellycompat's DisplayPreferences blobs ride the same table under synthetic
keys and keep working: they are that subsystem's storage rather than user
settings, and they move to dedicated storage in the follow-up rather than
being dropped here.
Also repoints the DisplayPreferences seed at the canonical resolver.
Resolved at profile scope with no device on purpose — Jellyfin clients do
not carry Silo's device identity, so a device override leaking into the
seed would hand one device's settings to every Jellyfin client on the
account.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
