refactor: introduce Instance connection lifecycle service

internal/instance/errors.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+// Failure contains only a safe operation message and a Condition reason.
+// Raw driver errors can contain credentials and must not escape through wrapping.
+type Failure struct {
+	Reason    string
+	Operation string
+}
+
+func (e Failure) Error() string           { return e.Operation }
+func (e Failure) ConditionReason() string { return e.Reason }