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>

[benbrandt]

Good point, likely left over from early auth method experiments.
The problem is we have some large clients in use requiring the current serialization method. We are working on hardening this up for unstable things in the future. But I am not sure this is worth it. We can clean up in the v2 implementation if necessaryu