Fix scrolled customization fixture timeout

Give the scrolled fixtures enough virtual time for the scrollbar hide and fade wait to complete.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: houghj16

src/vs/workbench/test/browser/componentFixtures/sessions/aiCustomizationManagementEditor.fixture.ts

@@ -2123,6 +2123,7 @@ export default defineThemedFixtureGroup({ path: 'chat/aiCustomizations/' }, {
 	// Scrolled-to-bottom variants — verify last items are fully visible above footer
 	PromptsTabScrolled: defineComponentFixture({
 		labels: { kind: 'screenshot' },
+		virtualTime: { durationMs: 1500 },
 		render: ctx => renderEditor(ctx, {
 			sessionResource: localSessionResource,
 			selectedSection: AICustomizationManagementSection.Prompts,
@@ -2132,6 +2133,7 @@ export default defineThemedFixtureGroup({ path: 'chat/aiCustomizations/' }, {
 
 	McpServersTabScrolled: defineComponentFixture({
 		labels: { kind: 'screenshot' },
+		virtualTime: { durationMs: 1500 },
 		render: ctx => renderEditor(ctx, {
 			sessionResource: localSessionResource,
 			selectedSection: AICustomizationManagementSection.McpServers,
@@ -2141,6 +2143,7 @@ export default defineThemedFixtureGroup({ path: 'chat/aiCustomizations/' }, {
 
 	PluginsTabScrolled: defineComponentFixture({
 		labels: { kind: 'screenshot' },
+		virtualTime: { durationMs: 1500 },
 		render: ctx => renderEditor(ctx, {
 			sessionResource: localSessionResource,
 			selectedSection: AICustomizationManagementSection.Plugins,