fix(overview): polish scorecard accessibility

中文：完善总览评分页的可访问性与视觉细节。

Author: edwingao28

packages/app/cypress/e2e/overview.cy.ts

@@ -15,14 +15,28 @@ describe('Executive overview', () => {
     });
   });
 
+  it('labels unavailable scorecard values for assistive technology', () => {
+    cy.visit('/overview');
+    cy.contains('tr', 'GLM5.2').within(() => {
+      cy.contains('No 8K/1K single-turn data').should('exist');
+      cy.get('td').eq(1).should('contain.text', 'Weighted score unavailable');
+      cy.get('td').eq(6).should('contain.text', 'Runner-up comparison unavailable');
+      cy.get('td').eq(7).should('contain.text', 'Freshness unavailable');
+    });
+  });
+
   it('shows a truthful empty state and a tracked detail link', () => {
     cy.visit('/overview');
     cy.contains('tr', 'GLM5.2').should('contain.text', 'No 8K/1K single-turn data');
     cy.contains('tr', 'Qwen3.5')
       .find('a[href^="/inference?"]')
       .should('have.attr', 'href')
       .and('include', 'i_seq=8k%2F1k');
-    cy.contains('tr', 'Qwen3.5').should('contain.text', 'Standard decode fallback');
+    cy.contains('tr', 'Qwen3.5')
+      .should('contain.text', 'Standard decode fallback')
+      .and('contain.text', '†')
+      .and('not.contain.text', '30:')
+      .and('not.contain.text', '100:');
     cy.get('[data-testid="overview-scorecard"]').should('contain.text', '—');
     cy.get('[data-testid="overview-scorecard"]').should('contain.text', '†');
     cy.get('[data-testid="overview-scorecard"] time').first().should('have.attr', 'datetime');
@@ -48,7 +62,12 @@ describe('Executive overview', () => {
     cy.visit('/zh/overview');
     cy.contains('h1', 'AI 推理高管总览').should('exist');
     cy.get('[data-testid="language-toggle"]').should('have.attr', 'href', '/overview');
-    cy.contains('tr', 'GLM5.2').should('contain.text', '暂无 8K/1K 单轮基准测试数据');
+    cy.contains('tr', 'GLM5.2').within(() => {
+      cy.contains('暂无 8K/1K 单轮基准测试数据').should('exist');
+      cy.get('td').eq(1).should('contain.text', '暂无加权评分');
+      cy.get('td').eq(6).should('contain.text', '暂无第二名对比');
+      cy.get('td').eq(7).should('contain.text', '暂无数据日期');
+    });
     cy.contains('加权评分').should('exist');
     cy.contains('第一名').should('exist');
   });

packages/app/cypress/fixtures/api/overview.json

@@ -241,7 +241,7 @@
         "decodeLabel": "MTP",
         "score": 1010,
         "tierValues": [
-          { "tier": 30, "value": 1200, "boundary": "interpolated" },
+          { "tier": 30, "value": 1200, "boundary": "clamped_low" },
           { "tier": 50, "value": 1000, "boundary": "interpolated" },
           { "tier": 75, "value": 800, "boundary": "interpolated" },
           { "tier": 100, "value": 600, "boundary": "interpolated" }
@@ -275,7 +275,7 @@
           "decodeLabel": "MTP",
           "score": 1010,
           "tierValues": [
-            { "tier": 30, "value": 1200, "boundary": "interpolated" },
+            { "tier": 30, "value": 1200, "boundary": "clamped_low" },
             { "tier": 50, "value": 1000, "boundary": "interpolated" },
             { "tier": 75, "value": 800, "boundary": "interpolated" },
             { "tier": 100, "value": 600, "boundary": "interpolated" }

packages/app/src/components/overview/overview-page.tsx

@@ -36,7 +36,11 @@ const STRINGS = {
     detailLink: 'View details',
     caption: 'Executive scorecard comparing the best serving platform for each active AI model.',
     scrollRegion: 'Scrollable executive inference scorecard',
-    unavailableSr: 'No reachable result at this tier',
+    missingPageDateSr: 'Latest official data date unavailable',
+    missingWeightedScoreSr: 'Weighted score unavailable',
+    missingRunnerUpSr: 'Runner-up comparison unavailable',
+    missingFreshnessSr: 'Freshness unavailable',
+    unavailableTierSr: 'No reachable result at this tier',
     clampedSr: 'Value clamped to the lowest observed interactivity point',
   },
   zh: {
@@ -63,7 +67,11 @@ const STRINGS = {
     detailLink: '查看详情',
     caption: '对比每个活跃 AI 模型最佳服务平台的高管评分表。',
     scrollRegion: '可横向滚动的 AI 推理高管评分表',
-    unavailableSr: '此档位无可达结果',
+    missingPageDateSr: '暂无最新官方数据日期',
+    missingWeightedScoreSr: '暂无加权评分',
+    missingRunnerUpSr: '暂无第二名对比',
+    missingFreshnessSr: '暂无数据日期',
+    unavailableTierSr: '此档位无可达结果',
     clampedSr: '该值采用已观测到的最低交互性数据点',
   },
 } as const;
@@ -89,7 +97,7 @@ function TierValue({
   strings: OverviewStrings;
 }) {
   if (!tierValue || tierValue.value === null || tierValue.boundary === 'unreachable') {
-    return <UnavailableValue label={strings.unavailableSr} />;
+    return <UnavailableValue label={strings.unavailableTierSr} />;
   }
 
   return (
@@ -165,7 +173,7 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
               {data.latestDate ? (
                 <time dateTime={data.latestDate}>{formatDate(data.latestDate, locale)}</time>
               ) : (
-                <UnavailableValue label={t.unavailableSr} />
+                <UnavailableValue label={t.missingPageDateSr} />
               )}
             </p>
           </div>
@@ -237,7 +245,7 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
                   >
                     <th
                       scope="row"
-                      className="sticky left-0 z-10 bg-card px-4 py-4 text-left align-top font-semibold transition-colors after:absolute after:inset-y-0 after:right-0 after:w-px after:bg-border group-hover:bg-muted/30 group-focus-within:bg-muted/30 motion-reduce:transition-none lg:px-6"
+                      className="sticky left-0 z-10 bg-card px-4 py-4 text-left align-top font-semibold transition-colors after:absolute after:inset-y-0 after:right-0 after:w-px after:bg-border group-hover:bg-muted group-focus-within:bg-muted motion-reduce:transition-none lg:px-6"
                     >
                       {model.modelLabel}
                     </th>
@@ -266,25 +274,6 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
                           {standardFallback && standardFallback !== winner ? (
                             <p className="text-xs leading-relaxed text-muted-foreground">
                               {t.standardFallback}: {standardFallback.hardwareLabel}
-                              {standardFallback.tierValues.some(
-                                (value) => value.boundary !== 'interpolated',
-                              ) ? (
-                                <span className="mt-0.5 block tabular-nums">
-                                  {standardFallback.tierValues
-                                    .filter((value) => value.boundary !== 'interpolated')
-                                    .map((value, index) => (
-                                      <span key={value.tier} className="whitespace-nowrap">
-                                        {index > 0 ? ' · ' : ''}
-                                        {value.tier}:{' '}
-                                        <TierValue
-                                          tierValue={value}
-                                          numberFormatter={numberFormatter}
-                                          strings={t}
-                                        />
-                                      </span>
-                                    ))}
-                                </span>
-                              ) : null}
                             </p>
                           ) : null}
                         </div>
@@ -296,7 +285,7 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
                       {winner ? (
                         numberFormatter.format(winner.score)
                       ) : (
-                        <UnavailableValue label={t.unavailableSr} />
+                        <UnavailableValue label={t.missingWeightedScoreSr} />
                       )}
                     </td>
                     {OVERVIEW_TIERS.map((tier) => (
@@ -310,7 +299,7 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
                     ))}
                     <td className="px-4 py-4 text-right align-top tabular-nums">
                       {model.runnerUpGapPercent === null ? (
-                        <UnavailableValue label={t.unavailableSr} />
+                        <UnavailableValue label={t.missingRunnerUpSr} />
                       ) : locale === 'zh' ? (
                         `较第二名高 ${numberFormatter.format(model.runnerUpGapPercent)}%`
                       ) : (
@@ -323,7 +312,7 @@ export function ExecutiveOverviewPage({ data, locale }: OverviewPageProps) {
                           {formatDate(winner.latestDate, locale)}
                         </time>
                       ) : (
-                        <UnavailableValue label={t.unavailableSr} />
+                        <UnavailableValue label={t.missingFreshnessSr} />
                       )}
                     </td>
                     <td className="px-4 py-4 text-right align-top">