SwiftUI resolves a text field's tint into a fixed caret colour when the
field takes focus and never refreshes it. The search field keeps focus
across hide and show, so after a Dark-to-Light switch the caret stayed
white and could not be seen. The panel now re-colours its field editor
with the dynamic textPrimary on every focus change.
Also carries a formatting pass over the AI chat, extension settings and
quick action sources and their tests.