feat: add typed error message templates and stable replay snapshots

httpx/context.go

@@ -314,11 +314,14 @@ func (c *Context) ResolveError(err error) *apierrors.APIError {
 // RecordError preserves failure semantics when a middleware commits buffered bytes.
 func (c *Context) RecordError(err error) { c.failure = c.ResolveError(err) }
 
+// RecordFailure propagates an already resolved failure without reapplying a
+// different parent/catalog policy. Used with committed or buffered responses.
+func (c *Context) RecordFailure(err *apierrors.APIError) { c.failure = err.Clone() }
+
 // Failure returns a detached description of a failure already handled by Context.
 func (c *Context) Failure() *apierrors.APIError {
 	if c.failure == nil {
 		return nil
 	}
-	copy := *c.failure
-	return &copy
+	return c.failure.Clone()
 }