The Vite minifier was tree-shaking the dev-login button because
devLoginConfig() always returned {enabled: false} when the
/internal/dev-login-config endpoint 404'd (which is the case on
canvas, where the endpoint isn't mounted).
That meant my prior 'default ON' fix never took effect — the useEffect
unconditionally flipped state to false within microseconds of mount.
Real fix: return {enabled: null} on absence. Only flip OFF when
endpoint explicitly says enabled=false. Otherwise honor the source
default.
Confidence: high
Scope-risk: narrow
