Firefox stores nsICookie::SAMESITE_UNSET (256) for a cookie that carried no
SameSite attribute, distinct from SAMESITE_NONE (0), an explicit opt-in to
cross-site use. The reader collapsed the unknown value onto Lax, and the
reviewed suggestion would have made it None — both change the cookie's
meaning. `ImportedCookie` now carries Electron's own `unspecified`, which lets
the target browser apply its default exactly as the source did, and both
engines map their "no attribute" sentinel (Firefox 256, Chromium -1) to it.

Also drops a doubled `/**` opener left above `cookieDatabaseCandidatePaths`.

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