Node's built-in fetch ignores HTTP_PROXY, so every harness request connected
directly regardless of what the user exported. Resolve one policy from the
launch environment and install it as undici's global dispatcher, then wire the
four surfaces a global dispatcher cannot reach: web_fetch's pinned transport,
the OTLP exporter's node:http agent, the E2B SDK's own proxy option, and the
environment a child process or worker thread is given.
Each outbound call site carries an egress test that drives its real code path
through a fake proxy; that measurement is what found the OTLP and E2B gaps.
