ASP.NET Core's cookie-handler IsAjaxRequest heuristic only checks
X-Requested-With (not Accept). Drop the third test (Accept: application/json
was assumed to → 401 but actually → 302) and the Location.ShouldBeNull
assertion on the XHR test (framework still writes Location alongside 401;
clients ignore it). Renamed _ajax_ → _xhr_ for accuracy. Design doc
updated to match.
Removes the JwtBearer parallel scheme + non-redirect 401 challenge that left
browsers staring at Chrome's HTTP_RESPONSE_CODE_FAILURE page on protected
GETs. JWT keeps minting (cookie payload only); cookie config flows through
the existing-but-unused OtOpcUaCookieOptions via PostConfigure (same pattern
ScadaBridge uses).