refactor(grades,diagnostic): 完成成绩和学情诊断模块审计 P1+P2 改进项

P1-1: 抽取 stats-service.ts，将 8 个统计计算纯函数从 data-access 层分离
P1-5: 创建 WidgetBoundary 组件 + 补齐 teacher 路由 loading.tsx/error.tsx (14 文件)
P1-6: 同步架构图文档 004/005，新增 stats-service 与 widget-boundary 节点
P2-1: 补充 a11y ARIA 属性（5 图表 role=img + aria-label，2 表格 caption，3 列表 role=list，3 按钮 aria-label）
P2-3: 修复班级报告 studentId 字段语义错误（schema 改为可空 + 迁移 + 代码适配）
P2-4: 修复 grade_managed scope 返回空数据（改为子查询 classes 表按 gradeId 过滤）
P2-5: 新增 /parent/diagnostic/ 页面（多子女学情诊断聚合 + loading + error）
P2-6: 统一 SearchParams 工具（student/grades 和 management/grade/insights 改用 @/shared/lib/search-params）

src/modules/diagnostic/components/mastery-radar-chart.tsx

@@ -35,35 +35,37 @@ export function MasteryRadarChart({ data }: MasteryRadarChartProps) {
       emptyDescription="No knowledge point mastery records found for this student."
       emptyClassName="h-60"
     >
-      <ComparisonRadarChart
-        data={chartData}
-        angleKey="shortName"
-        angleTickFontSize={11}
-        domain={[0, 100]}
-        tickCount={5}
-        showLegend={hasClassAverage}
-        heightClassName="mx-auto h-96 w-full max-w-lg"
-        gridStrokeDasharray="4 4"
-        series={[
-          {
-            dataKey: "student",
-            name: "Student",
-            color: "hsl(var(--primary))",
-            fillOpacity: 0.35,
-            strokeWidth: 2,
-            show: true,
-          },
-          {
-            dataKey: "classAverage",
-            name: "Class Avg",
-            color: "hsl(var(--chart-2))",
-            fillOpacity: 0.15,
-            strokeWidth: 2,
-            strokeDasharray: "4 4",
-            show: hasClassAverage,
-          },
-        ]}
-      />
+      <div role="img" aria-label={`知识点掌握度雷达图：${isEmpty ? "暂无数据" : `共 ${data.length} 个知识点的掌握度${hasClassAverage ? "（含班级平均对比）" : ""}`}`}>
+        <ComparisonRadarChart
+          data={chartData}
+          angleKey="shortName"
+          angleTickFontSize={11}
+          domain={[0, 100]}
+          tickCount={5}
+          showLegend={hasClassAverage}
+          heightClassName="mx-auto h-96 w-full max-w-lg"
+          gridStrokeDasharray="4 4"
+          series={[
+            {
+              dataKey: "student",
+              name: "Student",
+              color: "hsl(var(--primary))",
+              fillOpacity: 0.35,
+              strokeWidth: 2,
+              show: true,
+            },
+            {
+              dataKey: "classAverage",
+              name: "Class Avg",
+              color: "hsl(var(--chart-2))",
+              fillOpacity: 0.15,
+              strokeWidth: 2,
+              strokeDasharray: "4 4",
+              show: hasClassAverage,
+            },
+          ]}
+        />
+      </div>
     </ChartCardShell>
   )
 }

src/modules/diagnostic/components/report-list.tsx

@@ -157,6 +157,7 @@ export function ReportList({ reports }: ReportListProps) {
       ) : (
         <div className="rounded-md border bg-card">
           <Table>
+            <caption className="sr-only">学情诊断报告列表</caption>
             <TableHeader>
               <TableRow>
                 <TableHead>Type</TableHead>
@@ -175,7 +176,7 @@ export function ReportList({ reports }: ReportListProps) {
                   <TableCell>
                     <Badge variant="outline">{typeLabels[r.reportType] ?? r.reportType}</Badge>
                   </TableCell>
-                  <TableCell className="font-medium">{r.studentName}</TableCell>
+                  <TableCell className="font-medium">{r.studentName ?? (r.reportType === "class" ? "（班级报告）" : r.reportType === "grade" ? "（年级报告）" : "-")}</TableCell>
                   <TableCell>{r.period ?? "-"}</TableCell>
                   <TableCell className="text-right font-mono">
                     {r.overallScore !== null ? `${r.overallScore.toFixed(1)}%` : "-"}
@@ -195,6 +196,7 @@ export function ReportList({ reports }: ReportListProps) {
                             className="h-8 w-8 text-green-600"
                             onClick={() => setPublishId(r.id)}
                             title="Publish"
+                            aria-label={`发布报告 ${r.studentName}`}
                           >
                             <Send className="h-4 w-4" />
                           </Button>
@@ -205,6 +207,7 @@ export function ReportList({ reports }: ReportListProps) {
                           className="h-8 w-8 text-destructive"
                           onClick={() => setDeleteId(r.id)}
                           title="Delete"
+                          aria-label={`删除报告 ${r.studentName}`}
                         >
                           <Trash2 className="h-4 w-4" />
                         </Button>

src/modules/diagnostic/components/student-diagnostic-view.tsx

@@ -96,7 +96,7 @@ export function StudentDiagnosticView({ summary, reports, classAverageMastery }:
             {summary.strengths.length === 0 ? (
               <p className="text-sm text-muted-foreground">No strengths identified yet.</p>
             ) : (
-              <ul className="space-y-2">
+              <ul className="space-y-2" role="list" aria-label="优势知识点列表">
                 {summary.strengths.map((m) => (
                   <li key={m.knowledgePointId} className="flex items-center justify-between">
                     <span className="text-sm">{m.knowledgePointName}</span>
@@ -119,7 +119,7 @@ export function StudentDiagnosticView({ summary, reports, classAverageMastery }:
             {summary.weaknesses.length === 0 ? (
               <p className="text-sm text-muted-foreground">No weaknesses identified.</p>
             ) : (
-              <ul className="space-y-2">
+              <ul className="space-y-2" role="list" aria-label="薄弱知识点列表">
                 {summary.weaknesses.map((m) => (
                   <li key={m.knowledgePointId} className="flex items-center justify-between gap-2">
                     <div className="flex items-center gap-2 min-w-0">
@@ -162,7 +162,7 @@ export function StudentDiagnosticView({ summary, reports, classAverageMastery }:
             {latestReport.recommendations && latestReport.recommendations.length > 0 ? (
               <div>
                 <h4 className="mb-2 text-sm font-semibold">Recommendations</h4>
-                <ul className="space-y-1.5">
+                <ul className="space-y-1.5" role="list" aria-label="学习建议列表">
                   {latestReport.recommendations.map((rec, i) => (
                     <li key={i} className="text-sm text-muted-foreground">• {rec}</li>
                   ))}