fix(desktop): decode/encode changelog JSON as UTF-8 regardless of host locale (#9717) (#9885)

desktop-changelog.py called Path.read_text()/write_text() without an explicit
encoding, so native Windows Python with a non-UTF-8 default locale (e.g. GBK)
crashed with UnicodeDecodeError before reporting a changelog validation result.
Pass encoding="utf-8" on both calls to match CI and the checked-in files.

Author: kodjima33

.github/checks-manifest.yaml

@@ -34,6 +34,11 @@ checks:
     triggers: [".github/schemas/desktop-release-evidence-v1.schema.json", ".github/scripts/desktop_release_doctor.py", ".github/scripts/desktop_release_doctor_report.py", ".github/scripts/test_desktop_release_doctor.py", ".github/workflows/desktop_release_doctor.yml"]
     lanes: ["local", "ci"]
     reason: "advisory desktop release evidence and drift report"
+  - id: desktop-changelog-io-tests
+    command: ["python3", ".github/scripts/test_desktop_changelog.py"]
+    triggers: [".github/scripts/desktop-changelog.py", ".github/scripts/test_desktop_changelog.py", ".github/checks-manifest.yaml"]
+    lanes: ["local", "ci"]
+    reason: "#9717: changelog JSON I/O must decode/encode as UTF-8 regardless of contributor host locale"
   - id: agents-md-lean
     command: ["python3", ".github/scripts/check_agents_md_lean.py"]
     triggers: ["AGENTS.md", ".github/scripts/check_agents_md_lean.py"]

.github/scripts/desktop-changelog.py

@@ -24,14 +24,14 @@ class ChangelogError(Exception):
 
 def read_json(path: Path) -> object:
     try:
-        return json.loads(path.read_text())
+        return json.loads(path.read_text(encoding="utf-8"))
     except json.JSONDecodeError as exc:
         raise ChangelogError(f"{path} is not valid JSON: {exc}") from exc
 
 
 def write_json(path: Path, data: object) -> None:
     path.parent.mkdir(parents=True, exist_ok=True)
-    path.write_text(json.dumps(data, indent=2, ensure_ascii=False) + "\n")
+    path.write_text(json.dumps(data, indent=2, ensure_ascii=False) + "\n", encoding="utf-8")
 
 
 def normalize_changes(raw: object, path: Path) -> list[str]:

.github/scripts/test_desktop_changelog.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+"""Unit tests for desktop-changelog.py I/O encoding (stdlib unittest).
+
+Regression coverage for #9717: read_json/write_json must always use UTF-8 so a
+contributor on a non-UTF-8 host locale (e.g. GBK on native Windows Python) does
+not crash with a UnicodeDecodeError. The CI host is UTF-8, so a plain round-trip
+would not catch a missing encoding; these tests assert the encoding is forwarded
+on every platform.
+"""
+
+from __future__ import annotations
+
+import importlib.util
+import tempfile
+import unittest
+import unittest.mock
+from pathlib import Path
+
+_SPEC = importlib.util.spec_from_file_location(
+    "desktop_changelog", Path(__file__).with_name("desktop-changelog.py")
+)
+changelog = importlib.util.module_from_spec(_SPEC)
+_SPEC.loader.exec_module(changelog)
+
+
+class EncodingTests(unittest.TestCase):
+    def test_read_json_forces_utf8(self) -> None:
+        captured: dict[str, object] = {}
+        real_read_text = Path.read_text
+
+        def spy(self: Path, *args: object, **kwargs: object) -> str:
+            captured["encoding"] = kwargs.get("encoding")
+            return real_read_text(self, *args, **kwargs)
+
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "changelog.json"
+            path.write_text('{"note": "“curly”"}', encoding="utf-8")
+            with unittest.mock.patch.object(Path, "read_text", spy):
+                self.assertEqual(changelog.read_json(path), {"note": "“curly”"})
+        self.assertEqual(captured["encoding"], "utf-8")
+
+    def test_write_json_forces_utf8(self) -> None:
+        captured: dict[str, object] = {}
+        real_write_text = Path.write_text
+
+        def spy(self: Path, *args: object, **kwargs: object) -> int:
+            captured["encoding"] = kwargs.get("encoding")
+            return real_write_text(self, *args, **kwargs)
+
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "out" / "changelog.json"
+            with unittest.mock.patch.object(Path, "write_text", spy):
+                changelog.write_json(path, {"note": "“curly”"})
+        self.assertEqual(captured["encoding"], "utf-8")
+
+    def test_round_trip_preserves_non_ascii(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "changelog.json"
+            payload = {"note": "“curly” — café"}
+            changelog.write_json(path, payload)
+            self.assertEqual(changelog.read_json(path), payload)
+
+
+if __name__ == "__main__":
+    unittest.main()