test(plugin-manager): pin the title-only header motion away from font-dependent widths

Linux CI lays the title-only header at 470px with the actions beside the
title, while macOS wraps them, so that width depends on the platform
font. The title-only case now records 1280, 600, and 390px; the tabs case
keeps all four widths.

apps/web/tests/expected/plugin-manager/header-natural-motion.expected.md

@@ -2,7 +2,6 @@
 
 - Title / 1280px: resting title 28, actions 28, tabs none; pinned actions 16, tabs none, bar 64; stable range, reversible coordinates, same controls.
 - Title / 600px: resting title 28, actions 28, tabs none; pinned actions 16, tabs none, bar 64; stable range, reversible coordinates, same controls.
-- Title / 470px: resting title 28, actions 96, tabs none; pinned actions 16, tabs none, bar 64; stable range, reversible coordinates, same controls.
 - Title / 390px: resting title 28, actions 96, tabs none; pinned actions 16, tabs none, bar 64; stable range, reversible coordinates, same controls.
 - Tabs / 1280px: resting title 28, actions 28, tabs 96; pinned actions 17, tabs 16, bar 66; stable range, reversible coordinates, same controls.
 - Tabs / 600px: resting title 28, actions 97, tabs 96; pinned actions 17, tabs 16, bar 66; stable range, reversible coordinates, same controls.

apps/web/tests/plugin-sticky-motion.e2e.ts

@@ -82,7 +82,9 @@ it('preserves both header layouts and follows the scroll position without changi
           await page.locator('[data-plugin-package]').first().waitFor()
           await page.locator('[data-plugin-bar][data-natural]').waitFor()
           await page.evaluate(() => document.fonts.ready)
-          for (const width of [1280, 600, 470, 390]) {
+          // Without tabs, whether the actions fit beside the title at 470px depends on the platform font,
+          // so that width is pinned only with tabs.
+          for (const width of hasTabs ? [1280, 600, 470, 390] : [1280, 600, 390]) {
             await page.setViewportSize({ width, height: 480 })
             await scrollTo(page, 0)
             const resting = await reference(page, false)