Color panel: let the picker grow instead of scrolling

[JosVelasco]

What?

When a block's colour has poor contrast, the colour-settings popover can grow tall enough to get an internal scrollbar, hiding part of the contrast notice. This lets the popover grow to its natural height instead, so the whole picker — including the notice — stays readable at once.

Why?

The colour dropdown's Popover uses the size middleware, which caps the popover's height and adds overflow: auto when its content would run past the viewport. But size measures the space available from the popover's anchored position, before shift moves it up. So when the contrast notice made the panel taller, the popover was capped and given a scrollbar even though shift had already moved it to the top of the viewport with plenty of room for the full content below.

Observed in the editor: content needed ~500px and the viewport was ~732px with the popover sitting at the top, yet it was capped at ~477px and scrolled — leaving ~246px of empty space below the scrollbar.

How?

Set resize: false on this popover (keeping shift: true) so the size cap is not applied and the popover grows to its natural height; shift continues to keep it within the viewport.

Trade-off: without the cap, a popover taller than the entire viewport would clip rather than scroll. In practice this picker plus its notice is ~500px, well under a normal viewport, so there is ample headroom; the change trades a scrollbar that is essentially always avoidable for that rare edge case.

Testing Instructions

1. On a light-background theme (e.g. Twenty Twenty-Five), select a Paragraph.
2. Block → Typography → Color, and give it a light colour so the contrast notice appears (white text on a cream background is reliably "poor").
3. Observe the colour-settings popover with the notice at the bottom.

Expected: the whole popover — swatches, picker, and the full "poor contrast" notice — is visible with no internal scrollbar, and the popover stays within the viewport.

Screenshots or screencast

Verified in the editor: max-height becomes none, overflow visible, and the popover renders top 1px → bottom 501px within a 732px viewport (no scroll). Screenshot to be added.

AI assistance

• AI assistance: Yes
• Tool(s) used: Claude Code (Claude Opus 4.8)
• AI diagnosed the cause (measuring the popover geometry against the viewport), drafted the one-line change and this description, and the change has been reviewed by the contributor.