Phase A1: bootstrap Python ci_orchestrator package

- pyproject.toml (hatchling) with ruff/mypy/pytest dev deps
- src/ci_orchestrator/: config, credentials, backends (Protocol + WorkstationVmrunBackend), transport (WinRM via pypsrp, SSH via paramiko)
- CLI entry point with PoC 'wait-ready' subcommand (Windows + Linux guests)
- tests/python/: 35 unit tests, 83% coverage, all backends/transport mocked
- gitea/workflows/lint.yml: new 'python' job (ruff + mypy --strict + pytest --cov-fail-under=70)
- config.example.toml + README setup section + .gitignore Python entries

Neutral VmBackend Protocol prepared for Phase C ESXi extension.
See plans/implementation-plan-A-B.md step A1.

src/ci_orchestrator/backends/__init__.py

@@ -0,0 +1,30 @@
+"""VM backend implementations.
+
+The :class:`~ci_orchestrator.backends.protocol.VmBackend` Protocol defines
+the neutral interface every backend must satisfy. Phase A ships only the
+:class:`~ci_orchestrator.backends.workstation.WorkstationVmrunBackend`;
+Phase C will add an ESXi backend behind the same interface.
+"""
+
+from __future__ import annotations
+
+from ci_orchestrator.backends.protocol import VmBackend, VmHandle, VmState
+from ci_orchestrator.backends.workstation import WorkstationVmrunBackend
+
+__all__ = ["VmBackend", "VmHandle", "VmState", "WorkstationVmrunBackend", "load_backend"]
+
+
+def load_backend(config: object) -> VmBackend:
+    """Factory: pick a backend implementation from ``config.backend.type``.
+
+    Phase C hook: when the ESXi backend lands, this function will dispatch
+    on ``config.backend.type``. For now only ``workstation`` is supported.
+    """
+    backend_type = getattr(getattr(config, "backend", None), "type", "workstation")
+    if backend_type != "workstation":
+        raise NotImplementedError(
+            f"Backend type '{backend_type}' is not implemented. "
+            "Only 'workstation' is available in Phase A."
+        )
+    vmrun_path = getattr(config, "vmrun_path", None)
+    return WorkstationVmrunBackend(vmrun_path=vmrun_path)