The http.Server was built with only ReadHeaderTimeout set; the other three
timeouts were zero, which in net/http means no limit, so a peer could hold a
connection open past the header phase, responses had no write deadline, and
keep-alive connections were never reaped. ReadTimeout 15s, WriteTimeout 75s,
and IdleTimeout 120s now join ReadHeaderTimeout 10s as named constants.
WriteTimeout must stay above the 60s chimw.Timeout handler budget, because
net/http arms the write deadline once request headers are read; a test fails
the build if either number moves alone. The server literal moved into
newHTTPServer so the configuration can be asserted without binding a socket
(closes#99)
Model: opus-5
