fix: legacy style shorthand for a variable only declared

[paoloricciuti]

Svelte 5 rewrite

Closes #11417. The shorthand was not an Identifier in legacy_scope_tweaker so if the style shorthand was the only place where a declared variable was used the compiler was wrongly keep that variable as "normal" instead of "state" thus not updating the style on change.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 5299080

The changes in this PR will be included in the next version bump.

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[dummdidumm]

Thank you!