fix(www): de-duplicate footer chrome baselines (route-invariant chrome)

The footer is identical across routes for a given locale/theme/viewport,
so per-route footer snapshots are byte-identical and fail the
exact-duplicate baseline gate (#1230 M15). The footer now owns ONE
baseline per locale x theme x viewport (shot on the home route); the
docs sidebar keeps its per-route baselines because its section filtering
makes each route's chrome distinct. Desktop sidebar baselines were
regenerated under the fixed property-contract behavior (claim now
succeeds and the island actually hydrates, so the committed pixels
reflect the hydrated shell rather than the pre-fix stuck-SSR state).

Author: DevBot

www/e2e/visual-baselines.spec.ts

@@ -64,12 +64,15 @@ const sharedLocaleBaselines = new Set<string>([]);
 // (fullPage: false keeps the baseline stable across long pages and the
 // cinematic scroll surfaces), which is exactly how the page-bottom footer
 // regression shipped green. Dedicated chrome element snapshots close that
-// gap: the footer (every layout class) and the docs sidebar (desktop reading
-// layouts) own reviewed baselines without taking on fullPage flakiness.
+// gap: the docs sidebar (desktop reading layouts) owns a reviewed baseline
+// per reading route — its section filtering makes each route's chrome
+// distinct. The footer is route-invariant chrome, so it owns ONE baseline
+// per locale x theme x viewport (shot on the home route); per-route footer
+// snapshots are byte-identical and fail the exact-duplicate baseline gate.
 const chromeRoutes = [
-  { route: '/', sidebar: false },
-  { route: '/guide/getting-started', sidebar: true },
-  { route: '/architecture/dsd', sidebar: true },
+  { route: '/', sidebar: false, footer: true },
+  { route: '/guide/getting-started', sidebar: true, footer: false },
+  { route: '/architecture/dsd', sidebar: true, footer: false },
 ] as const;
 
 for (const locale of ['en', 'zh'] as const) {
@@ -80,7 +83,7 @@ for (const locale of ['en', 'zh'] as const) {
         await page.setViewportSize(viewport);
         await page.emulateMedia({ reducedMotion: 'reduce' });
         await page.addInitScript((value) => localStorage.setItem('open-theme', value), theme);
-        for (const { route, sidebar } of chromeRoutes) {
+        for (const { route, sidebar, footer } of chromeRoutes) {
           const localized = locale === 'en'
             ? route
             : route === '/'
@@ -90,12 +93,14 @@ for (const locale of ['en', 'zh'] as const) {
           await expect(page.locator('open-layout')).toBeVisible();
           const routeName = route === '/' ? 'home' : route.slice(1).replaceAll('/', '-');
           const chromeKey = `${locale}-${theme}-${viewport.name}-${routeName}`;
-          const footer = page.locator('.app-footer');
-          await footer.scrollIntoViewIfNeeded();
-          await expect(footer).toHaveScreenshot(`${chromeKey}-footer.png`, {
-            animations: 'disabled',
-            caret: 'hide',
-          });
+          if (footer) {
+            const footerLoc = page.locator('.app-footer');
+            await footerLoc.scrollIntoViewIfNeeded();
+            await expect(footerLoc).toHaveScreenshot(`${chromeKey}-footer.png`, {
+              animations: 'disabled',
+              caret: 'hide',
+            });
+          }
           // The sidebar is a desktop layout element; mobile collapses it into
           // the native disclosure covered semantically by site-chrome.spec.ts.
           if (sidebar && viewport.name === 'desktop') {