Clean up accessibility warnings

[theetrain]

Rarely, Svelte's a11y warnings are incorrect such as when it cannot detect valid children due to usage of <slot>. However, all warnings should be resolved properly.

Outcomes

• Remove all usage of autofocus and guide developers to set focus manually with ref
• Add a ref prop to all applicable components (part of Standardize props, events, and slots #1621)
• Remove and resolve <!-- svelte-ignore --> comments wherever possible