test+docs: startup-refusal exit code, real-body 413, pre-1.1.0 migration note

- main() exits 2 on permissive config (not just the predicate)
- 413 proven with an actual over-limit wire body, not header-only
- README: machine-user accounts need a seeded state.json mapping; only
  granthi-sync-e2e required it in beta

Co-Authored-By: Claude Fable 5 <[email protected]>

tests/test_server.py

@@ -364,6 +364,22 @@ class TestConfigPerms(unittest.TestCase):
         err = granthi_link.check_config_perms(self.tmp.name, euid=not_me)
         self.assertIn("owned by uid", err)
 
+    def test_main_exits_2_on_permissive_config(self):
+        """The refusal must actually stop startup (exit nonzero), not just
+        return a string -- verified through main()."""
+        with open(self.tmp.name, "w") as f:
+            json.dump({"gitea_base": "http://x", "admin_token": "t",
+                       "admin_login": "r", "admin_password": "p"}, f)
+        os.chmod(self.tmp.name, 0o644)
+        with mock.patch.object(granthi_link.sys, "argv",
+                               ["granthi_link.py", self.tmp.name]), \
+                mock.patch.object(granthi_link, "serve") as served, \
+                self.assertLogs("granthi-link", level="ERROR"):
+            with self.assertRaises(SystemExit) as cm:
+                granthi_link.main()
+        self.assertEqual(cm.exception.code, 2)
+        served.assert_not_called()  # never reached serve()
+
 
 class HandlerTestBase(ServiceTestBase):
     def setUp(self):
@@ -397,6 +413,18 @@ class TestBodyLimits(HandlerTestBase):
         self.assertEqual(status, 413)
         self.assertIn("too large", resp["error"])
 
+    def test_oversized_real_body_413(self):
+        """Send an actual over-limit payload on the wire (not just the
+        header), so the response is proven, not the predicate alone."""
+        body = json.dumps(
+            {"pad": "x" * (granthi_link.MAX_BODY_BYTES + 2000)}).encode()
+        self.assertGreater(len(body), granthi_link.MAX_BODY_BYTES)
+        status, resp = self.raw_post(
+            "/v1/link", body_bytes=body,
+            headers={"Content-Length": str(len(body)),
+                     "Content-Type": "application/json"})
+        self.assertEqual(status, 413)
+
     def test_missing_content_length_411(self):
         status, _ = self.raw_post("/v1/link")
         self.assertEqual(status, 411)