v1.78.0

What's changed

Condition hierarchy (#832):

• Add argument-error, a child condition of error. Cells.Read now raises argument-error.
• Add define-condition for user-defined conditions, and condition-is? to test a condition against a type and its ancestors.
• handler-bind now runs the most specific matching handler first.
• Add the handler-order lint check. It warns when a handler-bind binding comes after a binding for its own type or one of its ancestors, because such code ran differently under the old first-match order.
• Add rethrow :context and error-message for %w-style error wrapping. To give a wrapped error a different type, raise it explicitly.
• Document the condition hierarchy and handler order.