fix: fix videoAlpha being in percentage in older files, so loosen val…

[KFilosofov]

The purpose of this PR is to loosen the validation schema for the sb2 file types, the videoAlpha field is in percentage in older files so they fail being validated.

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[Copilot]

Pull request overview

This PR updates the Scratch 2.0 (SB2) JSON Schema definitions to accept older projects where the videoAlpha field is stored as a percentage rather than a 0–1 alpha value, preventing valid legacy SB2 files from failing validation.

Changes:

• Loosen SB2 schema constraint for videoAlpha by increasing its allowed maximum from 1 to 100.

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