[VS Code] Both gRPC and WebSocket connections fail in corporate proxy environments

Please reference this issue for logs and background.

User problem to solve

Users in corporate environments with proxy configurations cannot use GitLab DAP in VS Code with either gRPC or WebSocket connection types. While basic HTTP requests (curl) work through the proxy, both of the other connection methods fail.

User impact

• DAP is non-functional in these environments
• No working connection method available to users

Proposed Fix

If proxy settings are in use by the LsFetch client then default to use WebSockets workflow client by default when connecting to Duo Agent Platform.

Desired outcome

Users in corporate proxy environments can successfully use DAP (chat and flows) in VS Code using at least one of the connection methods.

• At least one connection method works in standard corporate proxy environments
• Clear error messages guide users through connection troubleshooting
• Extension provides network diagnostics or connection testing functionality