Proxy does not support dual-stack outbound — IPv6 CONNECT fails when client connects via IPv4

[Snypes88]

Description

The Agent Vault proxy listens on *:14322 (dual-stack), but outbound address family is tied to how the client connected:

Client connects via	IPv4 outbound	IPv6 outbound
127.0.0.1:14322	✅ Works	❌ Fails (HTTP 000)
[::1]:14322	❌ Fails	✅ Works

When a client connects over IPv4 and requests an IPv6 destination via CONNECT, the proxy fails to establish the outbound connection. This means HTTPS_PROXY=http://127.0.0.1:14322 breaks all IPv6 traffic through the proxy.

Steps to Reproduce

# IPv6 through IPv4 proxy — FAILS
curl -6 --proxy http://user:pass@127.0.0.1:14322 https://google.com/
# → HTTP 000 (curl error 7: failed to connect)

# IPv6 through IPv6 proxy — WORKS
curl -6 --proxy http://user:pass@[::1]:14322 https://google.com/
# → HTTP 301

Expected Behavior

The proxy should support dual-stack outbound regardless of which address family the client used to reach it. If a client connected via IPv4 requests an IPv6 destination, the proxy should establish an IPv6 outbound connection.

Environment

• Agent Vault v0.36.1
• Linux arm64, Debian 13
• Dual-stack VPS with both IPv4 and IPv6 connectivity

Workaround

Use --noproxy * for IPv6-specific requests, or switch the proxy URL to [::1] (but that breaks IPv4 outbound). Neither is a real solution.