React 19 dropped the no-arg useRef overload — the type-only useRef<T>()
form (no initial value) is gone, every call must pass an initial value.
The codebase had 15 occurrences of useRef<HTMLDivElement>() (DOM ref
pattern) all flagged by tsgo as 'Expected 1 arguments, but got 0'.
Mechanical sweep to useRef<HTMLDivElement>(null) — no behavior change,
React still hands out a ref object with .current set to null at mount.
Net tsgo error count: 57 -> 42.