feat: scaffolding an enum default select

[seankmartin]

Adds default value selection to enums via a selector

[Copilot]

Pull Request Overview

This PR adds default value selection functionality for enum-type annotation properties by implementing a dropdown selector that allows users to choose which enum value should be the default for new annotations.

• Implements a dropdown selector for setting default values on enum properties
• Updates default value handling logic to preserve valid defaults when enum values change
• Adds explanatory text about non-retroactive nature of schema default changes

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/ui/annotation_schema_tab.ts	Adds enum default selector UI component and updates default value preservation logic
src/ui/annotation_schema_tab.css	Adds styling for the new enum default selector component

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