fix(webchat): refresh bubbles on theme change

apps/shared/ClawdisKit/Tests/ClawdisKitTests/ChatThemeTests.swift

@@ -0,0 +1,29 @@
+@testable import ClawdisChatUI
+import Foundation
+import Testing
+
+#if os(macOS)
+import AppKit
+#endif
+
+#if os(macOS)
+private func luminance(_ color: NSColor) throws -> CGFloat {
+    let rgb = try #require(color.usingColorSpace(.deviceRGB))
+    return 0.2126 * rgb.redComponent + 0.7152 * rgb.greenComponent + 0.0722 * rgb.blueComponent
+}
+#endif
+
+@Suite struct ChatThemeTests {
+    @Test func assistantBubbleResolvesForLightAndDark() throws {
+        #if os(macOS)
+        let lightAppearance = try #require(NSAppearance(named: .aqua))
+        let darkAppearance = try #require(NSAppearance(named: .darkAqua))
+
+        let lightResolved = ClawdisChatTheme.resolvedAssistantBubbleColor(for: lightAppearance)
+        let darkResolved = ClawdisChatTheme.resolvedAssistantBubbleColor(for: darkAppearance)
+        #expect(try luminance(lightResolved) > luminance(darkResolved))
+        #else
+        #expect(Bool(true))
+        #endif
+    }
+}