POSIX popen routes via /bin/sh -c, so "2>&1" is a shell redirect. On
Windows we use CreateProcessW directly (no shell): curl receives "2>&1"
as a positional arg, treats it as a second URL, and fails with exit 3
"URL rejected: Bad hostname".
Stderr is already merged into the same pipe via STARTUPINFOW.hStdError
on Windows, so the redirect is also unnecessary there. Guard with
#ifndef _WIN32.
Also adds FN_HTTP_DEBUG env var to dump the cmdline + req.url for
future bug triage (zero-cost when unset).
Detected via agents_dashboard.exe --connect-test against
https://agents.organic-machine.com — same .exe with the fix now returns
"OK 11" in <2s.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
egutierrez
e387c91b4c