Update auth method terminal

[anaslimem]

Summary

Change AuthMethodTerminal.env from HashMap<String, String> to Vec<EnvVariable> for consistency with McpServerStdio.env.

Changes

Code Changes (src/agent.rs)

• Changed AuthMethodTerminal.env field type from HashMap<String, String> to Vec<EnvVariable>
• Updated builder method to accept Vec<EnvVariable>
• Removed unused HashMap import
• Updated test to use new EnvVariable struct

Documentation Updates

• docs/rfds/auth-methods.mdx: Updated JSON example and field description
• docs/protocol/draft/schema.mdx: Updated env type from object to EnvVariable[]

Before vs After

Code

// Before
pub env: HashMap<String, String>

// After  
pub env: Vec<EnvVariable>