<sl-dropdown> missing ARIA attributes until clicked

Describe the bug

<sl-dropdown>'s button trigger is missing aria-expanded and aria-haspopup attributes until the button is clicked, at which point the attributes are added. The attributes should be present before interacting with the button.

To Reproduce

Steps to reproduce the behavior:

1. Go to https://shoelace.style/components/dropdown/
2. Inspect the DOM of the <button> trigger of the first <sl-dropdown> instance and note that aria-expanded and aria-haspopup attributes are missing.
3. Click the <button>.
4. Inspect the DOM and see the button now has aria-expanded=true and aria-haspopup=true.

Demo

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Screenshots

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Browser / OS

• OS: Mac
• Browser: Chrome
• Browser version: 143

Additional information

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