feat: Cloud Hypervisor 执行器生产级 v1（cloud-hypervisor）

单任务单 VM：API 唤醒（preflight→vmm.ping→vm.create→vm.boot→SSH 就绪）、
暂停/快照/休眠等价/关闭/回收、预热快照池、每任务磁盘 copy、容量与磁盘配额门、
受控 egress fail-closed、VM 事件审计与分类失败；worker/server/autoscaler 接线
（executor=cloud-hypervisor，任务内 LLM 不可自选）；默认关闭，不进生产路由。
未做真实 VM 验证：生产主机与本 VM 均无 /dev/kvm、无嵌套虚拟化，验证为 mock +
干跑命令 + 单元测试；真 VM、快照恢复、压测、安全审计见
docs/chv-production-readiness.md。CI 账单故障仍是硬门禁，本提交只到 PR OPEN。

cloud/handler_project.py

@@ -67,9 +67,11 @@ class ProjectMixin:
             self._send_json(400, {"error": "name too long"})
             return
         executor = body.get("executor")
-        if executor is not None and executor not in ("local", "docker"):
+        if executor is not None and executor not in (
+                "local", "docker", "cloud-hypervisor"):
             self._send_json(400, {
-                "error": "executor must be local or docker"})
+                "error": "executor must be local, docker or "
+                         "cloud-hypervisor"})
             return
         try:
             branch = _validate_env_branch(body.get("branch"))