Every imported cookie passed `domain` to `session.cookies.set`. Electron reads
any `domain` as marking a domain cookie and normalizes it with a leading dot,
so every host-only row — Chromium stores those without one — came out scoped to
all subdomains of the host it had been confined to. It also rejects `__Host-`
cookies, which require `domain` to be absent.

`domain` is now carried only for rows Chromium marked as domain cookies, and
omitted from the write otherwise.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>