fix: prefer ts in unclear migration situations if tsconfig.json found

[dummdidumm]

Fixes #12880, relies on sveltejs/svelte#13929

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[ghostdevv]

ah

Error: packages/migrate check: migrations/svelte-5/index.js(175,61): error TS2353: Object literal may only specify known properties, and 'use_ts' does not exist in type '{ filename?: string | undefined; }'.

addressed