## Why
The proxy checks the requested host before opening the upstream
connection, but DNS can resolve an allowed hostname to a loopback,
private, or other non-public address after that first decision. Without
a final check on the actual socket target, a request that looks
acceptable at the hostname layer can still connect to a local service
once resolution completes.
## What changed
- add a shared TCP connector check for direct proxy egress
- use that path for HTTP, `CONNECT`, SOCKS5, and MITM upstream
connections
- keep configured upstream proxy hops on the existing proxy path
- add direct-connector coverage for allowed and rejected local targets
## Security impact
Direct proxy egress now rechecks the resolved socket address before
connecting, closing the gap between hostname policy evaluation and the
final network target.
## Verification
- `cargo test -p codex-network-proxy`
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Co-authored-by: Codex <noreply@openai.com>
