fix(tui): enable GitHub Copilot Enterprise authentication in /connect…

[Raviguntakala]

Problem

GitHub Copilot Enterprise authentication is missing in TUI /connect command. The CLI (auth login) supports enterprise login with deployment type selection and conditional prompts, but TUI /connect has no option for enterprise authentication at all.

Solution

Added enterprise authentication support to TUI /connect by implementing the same prompt collection logic as CLI:

• Added prompt collection loop to gather user inputs (deployment type, enterprise URL, etc.)
• Implemented conditional prompt logic for enterprise-specific fields
• OAuth callback now returns actual provider ID (github-copilot-enterprise vs github-copilot)

Changes

• dialog-provider.tsx - Added prompt collection before authorization
• auth.ts, server.ts - Return actual provider ID from OAuth callback
• dialog-model.tsx - Filter by provider.id instead of model.providerID
• provider.ts - Check both regular and enterprise auth for github-copilot plugin

Testing

• ✅ /connect with GitHub Copilot (public)
• ✅ /connect with GitHub Copilot Enterprise
• ✅ Enterprise models display correctly

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Note: If these changes are approved, I will raise a separate PR for Desktop app support.

Before :

https://github.com/user-attachments/assets/b7c35429-771e-4443-ae0e-db90160cc12d

After :

https://github.com/user-attachments/assets/88673ad8-4bf1-4485-8fcf-9f8512ba1e72