fix(presets): start fresh on a non-UTF-8 preset registry (#3955)

PresetRegistry._load() catches json.JSONDecodeError and
FileNotFoundError to start fresh on a corrupted or missing registry, but
a registry file with invalid UTF-8 bytes raised UnicodeDecodeError
before JSON parsing began, crashing every preset command.

Catch UnicodeDecodeError in the same clause: undecodable bytes are the
same corruption class as unparseable JSON. OSError stays uncaught on
purpose — the data may be intact on disk, and starting fresh would let a
later _save() wipe it (same fail-closed reasoning as the workflow
catalog cache loader).

Assisted-by: GitHub Copilot (model: claude-fable-5, autonomous)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/specify_cli/presets/__init__.py

@@ -550,7 +550,12 @@ class PresetRegistry:
             if not isinstance(data.get("presets"), dict):
                 data["presets"] = {}
             return data
-        except (json.JSONDecodeError, FileNotFoundError):
+        except (json.JSONDecodeError, UnicodeDecodeError, FileNotFoundError):
+            # Corrupted or missing registry, start fresh. A registry whose
+            # bytes cannot be decoded as UTF-8 is the same corruption class
+            # as malformed JSON — only the exception type differs. OSError is
+            # deliberately not caught: the data may be intact on disk, and
+            # starting fresh would let a later _save() wipe it.
             return {
                 "schema_version": self.SCHEMA_VERSION,
                 "presets": {}

tests/test_presets.py

@@ -515,6 +515,27 @@ class TestPresetRegistry:
         assert registry.list() == {}
         assert not registry.is_installed("test-pack")
 
+    def test_load_starts_fresh_for_non_utf8_registry(self, temp_dir):
+        """A registry file with undecodable bytes must start fresh, not raise.
+
+        ``_load()`` already treats malformed JSON as "corrupted registry,
+        start fresh", but a registry whose *bytes* cannot be decoded as UTF-8
+        raised a raw ``UnicodeDecodeError`` from the same boundary — the same
+        corruption class reaching a different exception type.
+        """
+        packs_dir = temp_dir / "packs"
+        packs_dir.mkdir()
+        (packs_dir / PresetRegistry.REGISTRY_FILE).write_bytes(
+            b"\xff\xfe not utf-8 \xc3\x28"
+        )
+
+        registry = PresetRegistry(packs_dir)
+
+        assert registry.data == {
+            "schema_version": PresetRegistry.SCHEMA_VERSION,
+            "presets": {},
+        }
+
     def test_add_and_get(self, temp_dir):
         """Test adding and retrieving a pack."""
         packs_dir = temp_dir / "packs"