workers: land host/pid/address columns with idempotent migration and pid_verified stale classification

- ensure_workers_table: new tables include host TEXT, pid BIGINT,
  address TEXT; old tables gain them via _ensure_hostpid_columns
  (PRAGMA column check, missing-only ALTER, old rows keep NULL,
  never fabricates host/pid). SQLite and Postgres share this path
  (PG via the db adapter's PRAGMA translation); POSTGRES_SCHEMA
  deliberately still excludes workers, which is volatile heartbeat
  data in UNMIGRATED_TABLES (adding it broke the P2 migration
  alignment tests, verified and reverted).
- heartbeat/register: given host/pid/address refresh, omitted
  values preserve the old row; address has no derived source.
  Local worker passes host_name + own pid; HTTP heartbeat only
  stores caller-supplied values, never the server's own.
- classify_stale_workers: kill only when age strictly exceeds the
  threshold AND host matches local host AND pid is proven dead;
  equal threshold, foreign host, missing pid, or live/unknown pid
  are list_only. Classification only, never kills, never matches
  by name/prefix, never touches infra containers.

cloud/worker.py

@@ -699,18 +699,26 @@ class Worker:
             register_worker(
                 self.db_path, self.worker_id,
                 executor=self._executor_name(), capacity=self.capacity,
-                running=self._running_count())
+                running=self._running_count(),
+                host=self.host_name, pid=os.getpid())
         except Exception as exc:
             log_event(self.logger, "worker_register_failed",
                       message="worker register failed: %s" % exc)
 
     def _registry_heartbeat(self):
-        """向控制面写注册表心跳（与文件心跳并行，失败只记日志）。"""
+        """向控制面写注册表心跳（与文件心跳并行，失败只记日志）。
+
+        host 用 self.host_name（autoscaler 显式传的宿主名；未传
+        时退化为 socket.gethostname()，容器内即容器名，与
+        worktree_host 同款 caveat），pid 用本进程号；两者每轮
+        刷新，供失联判定做本机 + pid 已死的 pid_verified 校验。
+        """
         try:
             heartbeat_worker(
                 self.db_path, self.worker_id,
                 executor=self._executor_name(), capacity=self.capacity,
-                running=self._running_count())
+                running=self._running_count(),
+                host=self.host_name, pid=os.getpid())
         except Exception as exc:
             log_event(self.logger, "worker_registry_heartbeat_failed",
                       message="worker registry heartbeat failed: %s" % exc)