Legacy foundation token override (backward compatibility)

The page overrides four legacy foundation token names on :root (see the <style> in <head>). Components read the new token names, but the override bridges make them honor the legacy names first.

Expected — overrides take effect:

1. All rounded corners (toolbar, buttons, dropdown panels) are SQUARE — --ck-border-radius: 0 (a re-defined token, override-only).
2. Spacing/padding is visibly LARGER — --ck-spacing-standard and --ck-spacing-large inflate the paddings and gaps that use them.
3. Small UI text is BIG — hover a toolbar button; the tooltip text uses --ck-tooltip-text-font-size, which bridges to --ck-font-size-tiny.

Without the bridges, none of these legacy overrides would have any effect. Note: these overrides reach the spots bridged to them, but --ck-spacing-standard does not rescale the whole spacing scale (that is now --ck-spacing-unit).