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/server.py

@@ -8641,9 +8641,12 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
 
     def _workers_heartbeat(self, user_id):
         """worker 心跳：body 含 worker_id（必填，缺了 400）与可选
-        executor/capacity/running。心跳本身就是注册：worker_id
-        不存在时自动注册，绝不 404。running 是 worker 上报的
-        当前占用槽数（启动中占位也算）；未给时保留旧值。"""
+        executor/capacity/running/host/pid/address。心跳本身就是
+        注册：worker_id 不存在时自动注册，绝不 404。running 是
+        worker 上报的当前占用槽数（启动中占位也算）；未给时保留
+        旧值。host/pid/address 只存调用方显式给的值：远程 worker
+        的 host/pid 绝不由 server 本机推导（server 的主机名/进程
+        号不是该 worker 的），未给时保留旧值。"""
         body, err = self._read_json()
         if err:
             self._send_json(400, {"error": err})
@@ -8670,10 +8673,29 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
             if running < 0:
                 self._send_json(400, {"error": "running must be >= 0"})
                 return
+        host = body.get("host")
+        if host is not None and not isinstance(host, str):
+            self._send_json(400, {"error": "host must be a string"})
+            return
+        pid = body.get("pid")
+        if pid is not None:
+            try:
+                pid = int(pid)
+            except (TypeError, ValueError):
+                self._send_json(400, {"error": "pid must be an integer"})
+                return
+            if pid <= 0:
+                self._send_json(400, {"error": "pid must be > 0"})
+                return
+        address = body.get("address")
+        if address is not None and not isinstance(address, str):
+            self._send_json(400, {"error": "address must be a string"})
+            return
         try:
             worker = _registry_heartbeat(
                 self.server.db_path, worker_id,
-                executor=executor, capacity=capacity, running=running)
+                executor=executor, capacity=capacity, running=running,
+                host=host, pid=pid, address=address)
         except ValueError as exc:
             self._send_json(400, {"error": str(exc)})
             return