fix: enable scrolling in workbench hover widget when content overflows

[galpodlipnik1]

Fixes #215972

Problem

The hover widget sets maxHeight on containerDomNode (which has overflow: hidden in CSS), but never constrains the DomScrollableElement wrapper inside it. Without a height constraint on the scrollable element, scrollHeight always equals clientHeight - the scrollbar never activates. The outer container's overflow: hidden simply clips the content invisibly.

Fix

• Store a reference to the status bar element (_statusBarElement) when actions are rendered in the constructor
• In adjustHoverMaxHeight, set maxHeight on scrollbar.getDomNode() equal to maxHeight - statusBarHeight, so DomScrollableElement detects the overflow and activates the scrollbar
• Reset scrollbar.getDomNode().style.maxHeight at the start of each layout() call

Testing

Hover over a terminal tab that has multiple extensions contributing to its environment (e.g. GitLens, GitHub Copilot) - enough to overflow the tooltip. The tooltip should now be scrollable with the mouse wheel instead of clipping the content.

[Copilot]

Pull request overview

Fixes a workbench hover regression where long hover content is clipped instead of being scrollable by attempting to correctly constrain the hover’s scrollable region when a max height is applied.

Changes:

• Store a reference to a rendered status bar row for height calculations.
• Reset the scrollable element’s maxHeight at the start of each layout() call.
• Subtract the status bar height from the hover’s computed max height and apply it to the scrollable region.

[galpodlipnik1]

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