Parent: #6871 | Epic: #6870

Description

Add the GitHub Copilot SDK Go dependency and create a CopilotClientManager wrapper that manages the copilot.Client lifecycle.

Tasks

• Add github.com/github/copilot-sdk/go@latest to go.mod
• Create pkg/llm/copilot_client.go with CopilotClientManager struct
• Implement lifecycle methods: Start(ctx), Stop(), GetAuthStatus(ctx)
• Implement ListModels(ctx) for model discovery
• Add IoC registration in cmd/container.go (alongside existing, not replacing)
• Unit tests

New File

pkg/llm/copilot_client.go

Notes

• SDK spawns copilot-agent-runtime process automatically on client.Start()
• Auth handled by SDK via Copilot subscription
• Must handle graceful errors when Copilot CLI is not available