Use configured HTTP transport for SSH metadata fetch

[arsenyinfo]

Summary

• getServerMetadata in experimental/ssh was using http.DefaultClient for the driver proxy metadata request, bypassing workspace TLS and proxy configuration from client.Config.
• Replace with &http.Client{Transport: client.Config.HTTPTransport} to respect custom TLS certs and proxy settings.

Test plan

• Verify SSH connect works with default config
• Verify SSH connect works behind corporate proxy with custom TLS certs