models.list -32603 in Kubernetes

# GitHub Copilot SDK Bug Report: models.list -32603 in Kubernetes

## Summary
GitHub Copilot SDK (Python, v1.0.1) fails with `JSON-RPC Error -32603: Failed to list models` when running in Kubernetes containers, despite:
- ✅ Valid GitHub token with copilot scope
- ✅ Network connectivity to all required endpoints
- ✅ Successful session creation
- ✅ Works perfectly in local development environment
- ✅ Direct REST API calls to `/models` endpoint succeed

## Environment
- **SDK**: github-copilot-sdk 1.0.1 (Python)
- **Runtime**: Docker container (python:3.11-slim)
- **Platform**: Kubernetes (AWS EKS, python:3.11-slim base image)
- **Token**: Valid GitHub token (gho_* format) with copilot scope verified via `curl` to API

## Error Details
```
Query execution fails with:
JSON-RPC Error -32603: Request models.list failed with message: Failed to list models

Stack trace indicates error occurs in:
- session.send_and_wait({"prompt": ...})
- SDK's bundled CLI subprocess RPC handler
- NOT in SDK Python code
```

## Reproduction

### Local (Works ✓)
```bash
# Windows local development
python -m uvicorn app.main:app --host 0.0.0.0 --port 8080
curl -X POST http://localhost:8080/prompt \
-H "Content-Type: application/json" \
-d '{"prompt":"Say hello","model":"gpt-5.3-codex"}'
# → Returns assistant response successfully
```

### Kubernetes (Fails ✗)
```bash
# Same code in K8s pod
kubectl exec -it -- python -c "
import asyncio
from copilot import CopilotClient
async def test():
async with CopilotClient(github_token='gho_...', use_logged_in_user=False) as client:
async with await client.create_session(model='gpt-5.3-codex') as session:
response = await session.send_and_wait({'prompt': 'hello'})
asyncio.run(test())
"
# → RuntimeError: Failed to list models (JSON-RPC -32603)
```

## Key Observations

1. **Session creation succeeds** - `CopilotClient.create_session()` completes without error
2. **Error happens during query execution** - `session.send_and_wait()` fails
3. **Error is from bundled CLI subprocess** - not SDK Python code
4. **All other RPC calls work** - session lifecycle, message sending succeed
5. **Direct API calls work** - `curl` to `api.githubcopilot.com/models` returns 200 OK
6. **Token is valid** - verified with `curl` to `api.github.com/user`

## Attempted Workarounds (All Failed)

| Workaround | Result |
|---|---|
| `on_list_models` handler callback | ❌ Still calls internal RPC during query |
| Monkey-patching `client.list_models` | ❌ SDK calls RPC through different path |
| Error filtering in event handlers | ❌ Error propagates before handlers |
| Retry logic on JsonRpcError | ❌ Retry fails identically |
| Using `model="auto"` | ❌ Same error |
| `use_logged_in_user=False` | ❌ Already set, still fails |
| Custom ModelInfo stubs | ❌ Callback not invoked for internal RPC |

## Root Cause Hypothesis

The SDK spawns a **bundled Copilot CLI subprocess** for internal JSON-RPC calls. This subprocess:

1. **Works locally** - has proper user context and environment
2. **Fails in K8s** - CLI subprocess cannot authenticate or reach API due to:
- Different user context (subprocess run as different UID?)
- Missing environment variables
- File system access restrictions
- Socket/IPC communication issues
- Home directory/config path issues

The `on_list_models` callback only helps with external calls; internal RPC calls during query execution bypass this handler.

## Requested Actions

1. **Acknowledge** - Confirm this is a known limitation in container environments
2. **Document** - Add warning to SDK docs about K8s/container deployment issues
3. **Fix** - Implement one of:
- Make CLI subprocess authentication environment-aware
- Allow disabling internal model validation via `COPILOT_CLI_SKIP_MODEL_VALIDATION`
- Pre-authenticate CLI subprocess in SDK initialization
- Make `on_list_models` handler apply to ALL internal list_models calls