fix(events): ignore non-UTF-8 event overrides (#3897)

Assisted-by: GitHub Copilot (model: GPT-5.6 Sol, autonomous)

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

src/specify_cli/events.py

@@ -737,8 +737,10 @@ def resolve_events(
     if override_file.exists():
         try:
             override = yaml.safe_load(override_file.read_text(encoding="utf-8")) or {}
-        except yaml.YAMLError:
-            logger.warning("Could not parse %s; ignoring override", override_file)
+        except (OSError, UnicodeError, yaml.YAMLError):
+            logger.warning(
+                "Could not read or parse %s; ignoring override", override_file
+            )
             override = {}
         integrations = override.get("integrations", {}) if isinstance(override, dict) else {}
         if isinstance(integrations, dict) and integration_key in integrations:

tests/integrations/test_events.py

@@ -128,6 +128,23 @@ class TestResolveEvents:
         )
         assert result == {}
 
+    def test_unreadable_yaml_override_keeps_prior_layers(self, tmp_path):
+        """An unreadable override is ignored like malformed YAML."""
+        override_file = tmp_path / ".specify" / "integration-events.yml"
+        override_file.parent.mkdir(parents=True, exist_ok=True)
+        override_file.write_bytes(b"\xff\xfe")
+
+        result = resolve_events(
+            "claude",
+            {"events": {"post_tool_use": {"command": "speckit.tdd.validate"}}},
+            tmp_path,
+            None,
+        )
+
+        assert result == {
+            "post_tool_use": [{"command": "speckit.tdd.validate"}]
+        }
+
     def test_no_config_no_events(self, tmp_path):
         """Safe fallback with empty config/options."""
         result = resolve_events("claude", None, tmp_path, None)