[WIP] Fix custom SVG icons to respect theme foreground color in tree view

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Custom SVG icons in tree view do not respect theme foreground color</issue_title>
<issue_description>Works correctly in the Activity Bar, but in the Tree View the icon is rendered black, likely because no theme foreground color is applied to the context:

When an explicit color is set, it is applied, indicating color leakage into the Tree View. This likely should not be allowed:

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