fix: strip /@fs prefix correctly on Windows when invoking read() in dev mode

[dummdidumm]

Windows absolute paths look like /@fs/C:/.. - when stripping the fs prefix, we need to remove the additional slash after the fs

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[Conduitry]

Can we mention in the title and in the changes etc that this is for read()? (I'm assuming it doesn't also affect anything else.) And is this only for dev mode?