feat: 导入导出错误信息 Markdown 渲染升级

Phase 1: 共用类型定义
- apps/server/src/common/import-result.types.ts — ImportRowError + ImportResult<T>
- apps/admin/src/types/import.ts — 前端对应类型 + ImportDisplayConfig

Phase 2: 后端增强
- students.service.ts — batchImport/matchImport 改为 ImportResult 格式
  · 每行跳过时收集 ImportRowError（code + reason）
  · reason 支持 markdown 标记（**字段名** / `值`）
- archive.service.ts — batchImportArchive 统一用 ImportResult 格式
  · 各 Sheet 错误使用标准 error code
- archive.controller.ts — 日志使用新的 success 字段

Phase 3: 前端基础
- 安装 react-markdown
- ImportResultModal 组件（共用导入结果弹窗）
  · Statistic 成功统计 + Table 错误明细
  · 原因列支持 react-markdown 渲染（粗体字段名、等宽代码值）
  · 错误类型用 Tag 颜色区分
- api/index.ts — 403 错误从 console.warn 改为 message.warning 用户可见

Phase 4: 前端集成
- Students/index.tsx — 替换硬编码导入结果弹窗
  · 删除'后端只返回统计汇总'注释和跳过原因 hardcode
  · 新格式自动使用 ImportResultModal，旧格式兼容
- StudentProfileContent/index.tsx — 替换内联导入 Modal 为 ImportResultModal

.agents/skills/subagent-driven-development/scripts/task-brief

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Extract one task's full text from an implementation plan into a file the
+# implementer reads in one call, so the task text never has to be pasted
+# through the controller's context.
+#
+# Usage: task-brief PLAN_FILE TASK_NUMBER [OUTFILE]
+# Default OUTFILE: <repo-root>/.superpowers/sdd/task-<N>-brief.md
+# (per worktree; concurrent runs in the same working tree share it).
+set -euo pipefail
+
+if [ $# -lt 2 ] || [ $# -gt 3 ]; then
+  echo "usage: task-brief PLAN_FILE TASK_NUMBER [OUTFILE]" >&2
+  exit 2
+fi
+
+plan=$1
+n=$2
+[ -f "$plan" ] || { echo "no such plan file: $plan" >&2; exit 2; }
+
+if [ $# -eq 3 ]; then
+  out=$3
+else
+  dir=$("$(cd "$(dirname "$0")" && pwd)/sdd-workspace")
+  out="$dir/task-${n}-brief.md"
+fi
+
+awk -v n="$n" '
+  /^```/ { infence = !infence }
+  !infence && /^#+[ \t]+Task[ \t]+[0-9]+/ {
+    intask = ($0 ~ ("^#+[ \t]+Task[ \t]+" n "([^0-9]|$)"))
+  }
+  intask { print }
+' "$plan" > "$out"
+
+if [ ! -s "$out" ]; then
+  echo "task ${n} not found in ${plan} (no heading matching 'Task ${n}')" >&2
+  exit 3
+fi
+
+echo "wrote ${out}: $(wc -l < "$out" | tr -d ' ') lines"