Update obsidian API typings to 1.13.1

Refreshes the obsidian package from 1.12.3 to 1.13.1. The new surface is
almost entirely the declarative settings framework (getSettingDefinitions,
SettingDefinition types), ConfirmationModal, and destructive-button styling;
no REST-relevant API changes. Typecheck and the full unit test suite pass
unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>