Variants: Implements validation hints to the variant selector (closes #19953)

[iOvergaard]

Description

Closes #19953

This pull request enhances the umb-workspace-split-view-variant-selector component by integrating contextual hint badges for variants. The main improvements involve consuming the hint context, mapping variant-specific hints, and displaying badges for relevant variants in the UI.

Hint context integration and display:

• Consumes the UMB_HINT_CONTEXT and observes descending hints, populating a _hintMap of variantId to UmbVariantHint for efficient lookup. [1] [2]
• Adds logic to display the highest-priority hint badge for inactive variants in both the main selector button and the variant list, using the new #renderHintBadge method. [1] [2] [3] [4]
• Ensures that each variant option in the list shows its associated hint badge when not active, improving user awareness of variant-specific issues or statuses.

Supporting logic and refactoring:

• Implements a type guard #isVariantHint to distinguish UmbVariantHint objects from other hints.
• Refactors rendering logic to use the hint map and active state consistently.

Screenshots

The validation hint happened on another variant than the active

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Go to the variant with a hint

[Copilot]

Pull Request Overview

This PR enhances the workspace split-view variant selector component by adding contextual hint badges that display validation errors and other statuses for inactive variants. This allows users to quickly identify which variants have issues without having to navigate to each variant individually.

Key changes:

• Integrates hint context consumption to track variant-specific hints
• Displays hint badges on inactive variants in both the main selector button and variant list
• Adds logic to prioritize hints by weight and filter for inactive variants

[leekelleher]

Tested out, works as expected! 🚀

(Apart from the cosmetics of the badge being cut-off, but we'll resolve that in due course)