453340e71e
Adds protected MapGet("/") in the test host plus three [Fact] methods
exercising the cookie scheme's challenge heuristic for the root route:
browser (Accept: text/html), AJAX (X-Requested-With: XMLHttpRequest),
and JSON (Accept: application/json) callers. Also adds a no-redirect
HttpClient helper so the 302 + Location can be asserted directly.