Migrate PostgreSQL before the identity probe in the real combo

Why: identity ensure no longer creates the schema, so the probe has to follow a real serve that applies migrations.
Evidence: SELF python3 -m py_compile tests/test_svc_realcombo.py. GATE run 2663 job 3839 failed on the previous head with identity table missing.
Impact: the PostgreSQL check still passes the DSN only through the environment, after serve has migrated.
Refs: #485
Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_svc_realcombo.py

@@ -21,7 +21,9 @@ import shutil
 import sqlite3
 import subprocess
 import tempfile
+import time
 import unittest
+import urllib.error
 import urllib.request
 from pathlib import Path
 
@@ -219,10 +221,40 @@ class RealComboTests(tsr.SvcAutoRecoverTests):
         命令行）；错 id fail-closed。"""
         rdm_bin = Path(REAL_RDM_BIN).resolve()
         data = self.root / "pgdata"
-        data.mkdir()
+        plugins = data / "plugins"
+        plugins.mkdir(parents=True)
         env = dict(os.environ)
         env["AGENT_SYSTEM_DSN"] = os.environ["AGENT_PG_TEST_DSN"]
+        env["RDM_DISABLE_EXEC_TOOLS"] = "1"
         env.pop("SVC_STUB_TRACE", None)
+        # 身份命令不建库、不迁移。先让 serve 把库迁到当前 schema，再 ensure/verify。
+        port = 9475
+        log = self.root / "pg-serve.log"
+        serve = subprocess.Popen(
+            [str(rdm_bin), "serve", "--addr", "127.0.0.1:%d" % port,
+             "--data", str(data), "--plugins", str(plugins), "--auth", "auto"],
+            env=env, stdout=log.open("w"), stderr=subprocess.STDOUT)
+        try:
+            up = False
+            for _ in range(50):
+                if serve.poll() is not None:
+                    break
+                try:
+                    urllib.request.urlopen("http://127.0.0.1:%d/" % port, timeout=1).close()
+                    up = True
+                    break
+                except urllib.error.HTTPError:
+                    up = True
+                    break
+                except OSError:
+                    time.sleep(0.1)
+            self.assertTrue(up, "serve 未完成迁移：\n%s" % log.read_text(errors="replace")[-1500:])
+        finally:
+            serve.terminate()
+            try:
+                serve.wait(timeout=5)
+            except subprocess.TimeoutExpired:
+                serve.kill()
         iid = "svc-realcombo-pg-%d" % os.getpid()
         run = lambda *a: subprocess.run(
             [str(rdm_bin), "identity", *a, "--instance-id", iid,