fix(GradientBlock): show colour codes on initial render

[peter-tudosa]

Main Changes

• Manifest: no settings are required, fixing saving a newly added gradient block
• the color badges weren't showing on first render because they were gated on a ref that is null during that render, and nothing re-rendered the block after the ref was assigned

Details

• Colour codes and labels now show on first load in view mode (width was read from a ref during render)
• Last badge no longer hangs outside the block; overflow is measured after layout
• Badge layout is derived with useMemo and no longer mutates the block settings
• parseGradientColorsToCss no longer sorts the settings array in place
• New shared useElementWidth hook
• Release entry for gradient-block