feat(portal-shell): 学生域全页面迁移与规范合规修复

- 学生域 32 页全量迁移(含作答/自动保存/提交/诊断)

- 补齐 4 个 MSW mock 缺口,修 diagnostic case 名

- 修 4 处 Tailwind 任意值;新增共享组件与路由

apps/portal-shell/src/features/teacher/ai/hooks/use-drag-position.ts

@@ -0,0 +1,130 @@
+"use client";
+
+import { useCallback, useEffect, useRef, useState } from "react";
+
+import type { Position } from "./use-position-persistence";
+import { clampPosition } from "./use-position-persistence";
+
+type DragState = {
+  active: boolean;
+  moved: boolean;
+  startX: number;
+  startY: number;
+  originX: number;
+  originY: number;
+  pointerId: number;
+};
+
+type DragCallbacks = {
+  /** 拖拽开始时触发（pointer down 后） */
+  onDragStart: () => void;
+  /** 拖拽释放时触发，moved 表示是否发生了实际移动 */
+  onRelease: (moved: boolean) => void;
+};
+
+/**
+ * 拖拽位置 Hook
+ *
+ * 处理 pointer 事件，跟踪拖拽状态与位置变化。
+ * 不处理边缘吸附、持久化等业务逻辑，通过回调委托给调用方。
+ */
+export function useDragPosition(
+  position: Position,
+  setPosition: React.Dispatch<React.SetStateAction<Position>>,
+  callbacks: DragCallbacks,
+): {
+  dragging: boolean;
+  handlers: {
+    onPointerDown: (e: React.PointerEvent<HTMLButtonElement>) => void;
+    onPointerMove: (e: React.PointerEvent<HTMLButtonElement>) => void;
+    onPointerUp: (e: React.PointerEvent<HTMLButtonElement>) => void;
+    onPointerCancel: () => void;
+  };
+} {
+  const [dragging, setDragging] = useState(false);
+  const dragStateRef = useRef<DragState>({
+    active: false,
+    moved: false,
+    startX: 0,
+    startY: 0,
+    originX: 0,
+    originY: 0,
+    pointerId: -1,
+  });
+  const callbacksRef = useRef(callbacks);
+  useEffect(() => {
+    callbacksRef.current = callbacks;
+  }, [callbacks]);
+
+  const onPointerDown = useCallback(
+    (e: React.PointerEvent<HTMLButtonElement>): void => {
+      // 仅主键响应拖拽
+      if (e.button !== 0 && e.pointerType === "mouse") return;
+      const s = dragStateRef.current;
+      s.active = true;
+      s.moved = false;
+      s.startX = e.clientX;
+      s.startY = e.clientY;
+      s.originX = position.x;
+      s.originY = position.y;
+      s.pointerId = e.pointerId;
+      try {
+        e.currentTarget.setPointerCapture(e.pointerId);
+      } catch {
+        // ignore
+      }
+      setDragging(true);
+      callbacksRef.current.onDragStart();
+    },
+    [position],
+  );
+
+  const onPointerMove = useCallback(
+    (e: React.PointerEvent<HTMLButtonElement>): void => {
+      const s = dragStateRef.current;
+      if (!s.active || e.pointerId !== s.pointerId) return;
+      const dx = e.clientX - s.startX;
+      const dy = e.clientY - s.startY;
+      // 阈值过滤微抖动
+      if (!s.moved && Math.abs(dx) + Math.abs(dy) < 4) return;
+      s.moved = true;
+      const next = clampPosition({
+        x: s.originX + dx,
+        y: s.originY + dy,
+      });
+      setPosition(next);
+    },
+    [setPosition],
+  );
+
+  const onPointerUp = useCallback(
+    (e: React.PointerEvent<HTMLButtonElement>): void => {
+      const s = dragStateRef.current;
+      if (!s.active || e.pointerId !== s.pointerId) return;
+      s.active = false;
+      setDragging(false);
+      try {
+        e.currentTarget.releasePointerCapture(e.pointerId);
+      } catch {
+        // ignore
+      }
+      callbacksRef.current.onRelease(s.moved);
+    },
+    [],
+  );
+
+  const onPointerCancel = useCallback((): void => {
+    dragStateRef.current.active = false;
+    setDragging(false);
+  }, []);
+
+  return {
+    dragging,
+    handlers: {
+      onPointerDown,
+      onPointerMove,
+      onPointerUp,
+      onPointerCancel,
+    },
+  };
+}