Builds on PR #1879's Copilot integration with critical auth improvements
modeled after opencode's implementation:
- Add hermes_cli/copilot_auth.py with:
- OAuth device code flow (copilot_device_code_login) using the same
client_id (Ov23li8tweQw6odWQebz) as opencode and Copilot CLI
- Token type validation: reject classic PATs (ghp_*) with a clear
error message explaining supported token types
- Proper env var priority: COPILOT_GITHUB_TOKEN > GH_TOKEN > GITHUB_TOKEN
(matching Copilot CLI documentation)
- copilot_request_headers() with Openai-Intent, x-initiator, and
Copilot-Vision-Request headers (matching opencode)
- Update auth.py:
- PROVIDER_REGISTRY copilot entry uses correct env var order
- _resolve_api_key_provider_secret delegates to copilot_auth for
the copilot provider with proper token validation
- Update models.py:
- copilot_default_headers() now includes Openai-Intent and x-initiator
- Update main.py:
- _model_flow_copilot offers OAuth device code login when no token
is found, with manual token entry as fallback
- Shows supported vs unsupported token types
- 22 new tests covering token validation, env var priority, header
generation, and integration with existing auth infrastructure
