fix: reject stale agent scaffolds

tests/test_template_init.py

@@ -1,8 +1,11 @@
 from __future__ import annotations
 
+import io
+import tarfile
 import unittest
 
 from agent_builder.tools import (
+    _assert_current_agent_project,
     _assert_current_a2a_init_template,
     _render_a2a_init_template,
 )
@@ -35,3 +38,23 @@ class TemplateInitTests(unittest.TestCase):
                 "agent.py": "from a2a_pack import A2AAgent",
                 "requirements.txt": "httpx>=0.27",
             })
+
+    def test_stale_agent_project_is_rejected(self) -> None:
+        bundle = _tarball({
+            "agent.py": "from a2a_pack import A2AAgent\n",
+            "requirements.txt": "httpx>=0.27\n",
+        })
+
+        with self.assertRaisesRegex(RuntimeError, "agent project is stale"):
+            _assert_current_agent_project(bundle)
+
+
+def _tarball(files: dict[str, str]) -> bytes:
+    buf = io.BytesIO()
+    with tarfile.open(fileobj=buf, mode="w:gz") as tf:
+        for path, text in files.items():
+            body = text.encode("utf-8")
+            info = tarfile.TarInfo(path)
+            info.size = len(body)
+            tf.addfile(info, io.BytesIO(body))
+    return buf.getvalue()