test: close unclosed file handles in tests (Path read/write)

Replace bare open().read()/write() in tests with Path.read_text/
write_text (or json.loads over read_text); the five remaining
open(...).close() empty-file creations become Path.write_text('').
No assertion, predicate, or production code changed; no behaviour
change beyond closing the handle deterministically.

Long-function splits and server.py module split intentionally not
included: the longest functions (_dispatch, _create_task,
_dispatch_project, ~375-395 lines in a 10430-line server.py) are
central routing/creation paths, and splitting them is not low-risk;
see PR body.

cloud/tests/test_skill_seed_worker.py

@@ -35,8 +35,9 @@ class SkillSeedHelperTestCase(unittest.TestCase):
         for name in ("live-info", "document-tools"):
             d = os.path.join(src, name)
             os.makedirs(d, exist_ok=True)
-            open(os.path.join(d, "SKILL.md"), "w").write(
-                "---\nname: %s\ndescription: test\n---\nbody\n" % name)
+            Path(os.path.join(d, "SKILL.md")).write_text(
+                "---\nname: %s\ndescription: test\n---\nbody\n" % name,
+                encoding="utf-8")
         return src
 
     def test_copy_idempotent_and_missing_source(self):
@@ -58,10 +59,10 @@ class SkillSeedHelperTestCase(unittest.TestCase):
         ensure_codex_home_skills(home, src)
         dest = os.path.join(home, "skills",
                             "live-info", "SKILL.md")
-        open(dest, "w").write("tenant edited version\n")
+        Path(dest).write_text("tenant edited version\n", encoding="utf-8")
         out = ensure_codex_home_skills(home, src)
         self.assertEqual(out["skills_skipped_differ"], ["live-info"])
-        self.assertEqual(open(dest).read(), "tenant edited version\n")
+        self.assertEqual(Path(dest).read_text(encoding="utf-8"), "tenant edited version\n")
 
     def test_real_pack_lists_all_skills(self):
         names = [n for n, _p in list_skills()]
@@ -78,13 +79,13 @@ class WorkerSkillSeedTestCase(unittest.TestCase):
         init_db(self.db_path)
         self.template_home = os.path.join(self.tmp.name, "tpl-home")
         os.makedirs(self.template_home)
-        open(os.path.join(self.template_home, "config.toml"),
-             "w").write('[model_provider.xcmapi]\n'
-                         'base_url="https://xcmapi.org/v1"\n')
+        Path(os.path.join(self.template_home, "config.toml")).write_text(
+            '[model_provider.xcmapi]\n'
+            'base_url="https://xcmapi.org/v1"\n', encoding="utf-8")
         self.template_repo = os.path.join(self.tmp.name, "tpl-repo")
         os.makedirs(os.path.join(self.template_repo, ".git"))
-        open(os.path.join(self.template_repo, "sample.py"),
-             "w").write("def add(a, b):\n    return a + b\n")
+        Path(os.path.join(self.template_repo, "sample.py")).write_text(
+            "def add(a, b):\n    return a + b\n", encoding="utf-8")
 
     def tearDown(self):
         self.tmp.cleanup()
@@ -115,22 +116,22 @@ class WorkerSkillSeedTestCase(unittest.TestCase):
         for name in ("live-info", "document-tools", "image-workflow"):
             path = self._skill_path(dirs, name)
             self.assertTrue(os.path.exists(path), path)
-            self.assertIn("name: %s" % name, open(path).read())
+            self.assertIn("name: %s" % name, Path(path).read_text(encoding="utf-8"))
 
     def test_flag_on_seeds_software_engineering_and_user_edit_survives(self):
         worker = self._worker(seed_skills=True)
         dirs = worker._tenant_dirs("projA")
         path = self._skill_path(dirs, "software-engineering")
         self.assertTrue(os.path.exists(path), path)
-        text = open(path).read()
+        text = Path(path).read_text(encoding="utf-8")
         self.assertIn("name: software-engineering", text)
         # v0.2 P0-1: the appendix travels inside SKILL.md itself,
         # because skill_seed only copies SKILL.md, not templates/.
         self.assertIn("附录角色：00-coordinator", text)
         self.assertIn("附录角色：08-shared-core", text)
-        open(path, "w").write("tenant edited version\n")
+        Path(path).write_text("tenant edited version\n", encoding="utf-8")
         worker._tenant_dirs("projA")
-        self.assertEqual(open(path).read(), "tenant edited version\n")
+        self.assertEqual(Path(path).read_text(encoding="utf-8"), "tenant edited version\n")
 
     def test_old_tenant_merges_and_user_edit_survives(self):
         worker = self._worker()
@@ -139,9 +140,9 @@ class WorkerSkillSeedTestCase(unittest.TestCase):
         worker2._tenant_dirs("projA")
         path = self._skill_path(dirs, "live-info")
         self.assertTrue(os.path.exists(path))
-        open(path, "w").write("tenant edited version\n")
+        Path(path).write_text("tenant edited version\n", encoding="utf-8")
         worker2._tenant_dirs("projA")
-        self.assertEqual(open(path).read(), "tenant edited version\n")
+        self.assertEqual(Path(path).read_text(encoding="utf-8"), "tenant edited version\n")
 
 
 if __name__ == "__main__":