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/server.py

@@ -494,6 +494,9 @@ def _task_worktree_for_files(server, task):
     """
     if task.get("executor") == "cloud":
         return None, (409, "cloud task worktrees are not on this host")
+    if task.get("executor") == "cloud-hypervisor":
+        return None, (409, "cloud-hypervisor task worktrees are "
+                           "inside the VM, not on this host")
     worktree_host = task.get("worktree_host")
     if worktree_host and worktree_host != socket.gethostname():
         return None, (409, "task worktree is on host %s;"
@@ -1550,7 +1553,7 @@ def _default_executor():
     raw = raw.strip()
     if raw == "":
         return None
-    if raw in ("local", "docker", "cloud"):
+    if raw in ("local", "docker", "cloud", "cloud-hypervisor"):
         return raw
     return "docker"
 
@@ -2492,9 +2495,11 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
             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"))
@@ -4248,12 +4253,15 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
             self._send_json(400, {"error": "priority must be an integer"})
             return
         # executor 可选：None 表示任意 worker 可认领；指定时只能是
-        # local/docker/cloud，非法值 400 且不建任务。
+        # local/docker/cloud/cloud-hypervisor，非法值 400 且不建任务。
+        # cloud-hypervisor 是创建层可见的调度选择（任务内 LLM
+        # 绝不能自选它，见 sandbox.py 该类 docstring）。
         executor = body.get("executor")
         if executor is not None and executor not in (
-                "local", "docker", "cloud"):
+                "local", "docker", "cloud", "cloud-hypervisor"):
             self._send_json(400, {
-                "error": "executor must be local, docker or cloud"})
+                "error": "executor must be local, docker, cloud or "
+                         "cloud-hypervisor"})
             return
         # 任务级选项：model 不做白名单（中转目录会变，下拉只是
         # 建议值）；effort 必须是 codex 的 effort 档位；approval
@@ -4481,6 +4489,10 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                 self._send_json(400, {
                     "error": "附件不支持 cloud 执行器"})
                 return
+            if executor == "cloud-hypervisor":
+                self._send_json(400, {
+                    "error": "附件不支持 cloud-hypervisor 执行器"})
+                return
             conn0 = self._db()
             try:
                 brow = conn0.execute(
@@ -5893,6 +5905,10 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
         if executor == "cloud":
             return (409, "thread ops are local-executor only;"
                     " cloud task threads are not on this host")
+        if executor == "cloud-hypervisor":
+            return (409, "thread ops are local-executor only;"
+                    " cloud-hypervisor task threads live inside"
+                    " the VM, not on this host")
         worktree_host = task.get("worktree_host")
         if worktree_host and worktree_host != socket.gethostname():
             return (409, "task worktree is on host %s;"