fix(storybook): refine responsive page inner width

- Story page Inner side margin: 16px up to a 480px viewport, linear to 60px at 768px, 60px beyond (no width jump)
- Follow the 60px margins: Responsive 1920 row from a 2040px page (was 2000px); property compare 3 columns from 1125px, 2 columns from 787px (was 1080 / 720)
- SW browser tests: drop the removed --sb-page-max-width override, compare thresholds 787 / 1125

packages/sw/tests/text-weight.browser.mjs

@@ -140,8 +140,8 @@ await page.keyboard.press('Escape')
 report.reference = { more: refMore[0], documents: refDocs[0], viewerItem: refViewerItem[0], viewerLabel: refViewerLabel[0] }
 
 await goto('sw-viewer--viewer-header')
-// The 1440px Story frame at full width (as the viewer suites): the header has room for every label.
-await page.addStyleTag({ content: '.sb-page { --sb-page-max-width: 100vw; }' }); await page.waitForTimeout(200)
+// The 1440px Story frame at full width (the 1920px page's Inner is 1800px): the header has room for every label.
+await page.waitForTimeout(200)
 const vh = page.locator('.hm-sw-viewer-header').first()
 const vNames = await styles('.hm-sw-viewer-header >> nth=0 >> :is(.hm-sw-header__document-name, .hm-sw-viewer-header__document-name, .hm-sw-viewer-header__label, .hm-sw-viewer-header__tab)')
 report.viewer = vNames