Vue: script vs template visibility for noUnusedEmitDeclarations

[sam-parsons]

Porting vue/no-unused-emit-declarations (#6306) runs into a structural point: JS lint rules see the <script> / <script setup> block, while template markup is handled separately (biome_js_analyze vs biome_html_analyze). A rule that only inspects the script cannot see $emit('…') (or equivalent) in <template>, so it can false-positive when an emit is only used from the template.

Questions for maintainers

1. Is there an existing way for a JS rule to account for template-side emit usage that we should use?
2. If not, is a script-only implementation acceptable for now, with the limitation documented in the rule’s rustdoc?

A short answer on (1)/(2) would unblock implementation scope for the issue above.