fix: update DisplayMode import in PulsarSettingsTest to match relocated class

The DisplayMode class was moved from ai.platon.pulsar.browser.common to
ai.platon.pulsar.api.model, but the test still imported the old package.
This caused 7/12 tests to fail with AssertionFailedError comparing two
different DisplayMode enum types.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: insidegalaxyeye

pulsar-core/pulsar-skeleton/src/test/kotlin/ai/platon/pulsar/skeleton/PulsarSettingsTest.kt

@@ -1,7 +1,7 @@
 package ai.platon.pulsar.skeleton
 
 import ai.platon.pulsar.api.InteractSettings
-import ai.platon.pulsar.browser.common.DisplayMode
+import ai.platon.pulsar.api.model.DisplayMode
 import ai.platon.pulsar.common.browser.InteractLevel
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertNull