refactor(cleanup): remove legacy CLI and complete EvoAgent migration cleanup

- Delete backend/cli.py and all CLI-specific tests (test_cli.py,
  test_openclaw_cli_service.py, test_skills_cli.py)
- Remove evotraders console script from pyproject.toml
- Update README/CLAUDE.md to reference python backend/main.py instead of CLI
- Add pytest-asyncio to dev dependencies
- Enhance EvoAgent with reload_runtime_assets and backward-compat attrs
- Align tests with updated API semantics and gateway process models

Constraint: CLI is deprecated in favor of split-service runtime model
Confidence: high
Scope-risk: moderate

backend/tests/test_service_clients.py

@@ -25,6 +25,8 @@ class _DummyAsyncClient:
 
     async def get(self, path, params=None):
         self.calls.append(("get", path, params))
+        if path == "/sessions/main/session-1":
+            return _DummyResponse({"session": {"key": "main/session-1", "agentId": "main"}})
         return _DummyResponse({"path": path, "params": params})
 
     async def post(self, path, json=None):