code-to10 v4 coverage thickening: 219 new assertion tests (batches A/B1/C/D1-D6)

Baseline merge head e5ff26a: 28144 stmts, 2807 missing, exact 90.0263%, margin +7.
After thickening (full run): 2350 missing, exact 91.6501%, margin +464.
Full suite 3516 items: 3509 pass, 1 failure (pre-existing November date
failure, untouched), 6 skipped. No production code changed.

cloud/tests/test_v2cov_gaps_d4.py

@@ -0,0 +1,85 @@
+"""Coverage batch v4-D4: cloud/server.py dispatch-safe/upload branches
+and cloud/ledger_outbox.py replay rewrite.
+
+Stubbing discipline: the method under test is never stubbed. Patched
+collaborators are: _dispatch / _send_json / _read_body / parse_multipart
+/ parse_paths_field (sinks and data providers). Every assertion reads a
+real return value, a real captured response, or a real file.
+"""
+
+import json
+import os
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+from unittest import mock
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(REPO_ROOT))
+
+from cloud import server as server_mod
+from cloud.ledger_outbox import replay_failures
+
+
+class DispatchSafeTestCase(unittest.TestCase):
+    def test_dispatch_and_send_both_raise_swallowed(self):
+        # 2310-2311: _dispatch raising and the 500 fallback also raising.
+        handler = object.__new__(server_mod.CloudControlPlaneHandler)
+        handler._responded = False
+        handler.path = "/x"
+        handler._dispatch = mock.Mock(
+            side_effect=RuntimeError("dispatch down"))
+        handler._send_json = mock.Mock(
+            side_effect=RuntimeError("send down"))
+        handler._dispatch_safe("GET")
+        handler._send_json.assert_called_once_with(
+            500, {"error": "internal_error"})
+
+
+class UploadMismatchTestCase(unittest.TestCase):
+    def test_paths_files_count_mismatch(self):
+        # 3149
+        handler = object.__new__(server_mod.CloudControlPlaneHandler)
+        handler.headers = {"Content-Type": "multipart/form-data",
+                           "Content-Length": "10"}
+        handler._read_body = mock.Mock(return_value=b"body")
+        sent = []
+        handler._send_json = lambda code, payload: sent.append(
+            (code, payload))
+        with mock.patch.object(
+                server_mod, "parse_multipart",
+                return_value=({}, [("a", b"x"), ("b", b"y")])):
+            with mock.patch.object(
+                    server_mod, "parse_paths_field",
+                    return_value=["only-one"]):
+                handler._create_upload("u1")
+        self.assertEqual(sent, [(400, {"error": "附件路径与文件数量不一致"})])
+
+
+class OutboxReplayTestCase(unittest.TestCase):
+    def test_failed_record_rewritten_back(self):
+        # 170: a failed replay row is rewritten into the outbox file.
+        with tempfile.TemporaryDirectory() as tmp:
+            path = os.path.join(tmp, "outbox.jsonl")
+            good = {"task_id": "t1", "outcome": "success"}
+            bad = {"task_id": "t2", "outcome": "failure"}
+            with open(path, "w", encoding="utf-8") as f:
+                f.write(json.dumps(good) + "\n")
+                f.write(json.dumps(bad) + "\n")
+
+            def _record(conn, task_id, outcome, is_defect=False):
+                if task_id == "t2":
+                    raise RuntimeError("ledger down")
+
+            stats = replay_failures(path, None, record_fn=_record)
+            self.assertEqual(stats["replayed"], 1)
+            self.assertEqual(stats["failed"], 1)
+            self.assertEqual(stats["remaining"], 1)
+            with open(path, encoding="utf-8") as f:
+                rows = [json.loads(line) for line in f if line.strip()]
+            self.assertEqual(rows, [bad])
+
+
+if __name__ == "__main__":
+    unittest.main()