docs: clarify event-driven action examples

[aose-yuu]

Purpose

Clarify the createEvents controlled molecule example so child molecules expose user intent actions instead of owner-style setters.

Summary

• Uses open, close, and toggle as the public dialog actions.
• Keeps update:open as the event-driven controlled value notification.
• Clarifies that action names can express user intent while isOpen remains the read model.
• Docs-only change; release is intentionally deferred.

Verification

• pnpm -s cicheck