RequestStreamAsync went through RequestAsync, which sends with the
default HttpCompletionOption.ResponseContentRead - so the whole body was
downloaded before the task resolved, and the "stream" handed back was
the buffer. A response that never ends (NDJSON, SSE, a chunked long
poll) therefore never resolved at all.
It also did `using var response`, disposing the response and with it the
content stream, before returning that stream to the caller. That second
bug hid the first: you could not read the stream far enough to notice
the buffering.
Send with ResponseHeadersRead and return a stream that owns the
HttpResponseMessage and disposes it with itself. RequestAsync's
signature is untouched, so no Sandbox.Access change is needed, and the
consumer side (System.IO.Stream.*, StreamReader) was already
whitelisted. Validation is unaffected: SboxHttpHandler runs
Http.IsAllowedAsync before every send, redirects included, all before
the headers come back.
WebTests.HttpStreamTest serves paced chunked NDJSON on localhost:8080 (a
port Http.IsAllowed accepts) and asserts the call returns before the
body ends, that the lines arrive spread across it rather than at once,
and that a non-2xx still throws.
* Move all unit tests to Engine/Tests
* Fix Margin.EdgeSubtract
* Fix Capsule.Contains
* EnvironmentVariables.Remove if it's null
* Fixed ray trace never returning startedsolid
* Fix HistoryList.Navigate on empty list
* Fix GameObject.WorldPosition accepting NaNs
* Fix flex: initial expanding to the wrong grow/shrink
* Translation.TryConvert shouldn't throw on invalid enum strings
* Skip sound file tests on machines with no audio device
