fix invalid negative values in sourcemap column indexes

[dominikg]

• check for invalid index values in decoded sourcemaps of existing samples
• find and fix why existing sourcemap tests did not detect this ( mappings should be traced back more strictly) -> existing tests never tracked the script tag itself
• find and fix underlying issue (fixed by fix: adjust loc property of Program nodes created from <script> elements #17428 )

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Playground

pnpm add https://pkg.pr.new/svelte@17167

[ArtskydJ]

This PR appears to be related to #17003.