Filter invalid nested drag targets before collision selection

packages/dnd/test/manager-lifecycle.test.ts

@@ -12,7 +12,7 @@ const compiled = new Bun.Transpiler({ loader: "ts" })
 function fixture(overrides: Partial<DndManagerOptions> = {}) {
   const listeners: Record<string, (event: any) => any> = {};
   const announcements: DndAnnouncement[] = [];
-  const instances: Array<{ destroyed: number }> = [];
+  const instances: Array<{ destroyed: number; input: any }> = [];
   let managerDestructions = 0;
   class Backend {
     monitor = {
@@ -26,7 +26,7 @@ function fixture(overrides: Partial<DndManagerOptions> = {}) {
   }
   class Sortable {
     destroyed = 0;
-    constructor() {
+    constructor(public input: any) {
       instances.push(this);
     }
     destroy() {
@@ -94,6 +94,21 @@ test("late drop resolution cannot clear or announce a newer gesture", async () =
   ]);
 });
 
+test("collision candidates exclude overlapping ancestors and invalid destinations before sorting", () => {
+  const f = fixture({ accept: (_ids, to) => to.group !== "blocked" });
+  const child = {} as HTMLElement;
+  f.manager.registerSortable({ id: "child", group: "content", index: 0, element: child, type: "text" });
+  f.manager.registerSortable({ id: "parent", group: "root", index: 0, element: { contains: (element: unknown) => element === child } as HTMLElement });
+  f.manager.registerSortable({ id: "sibling", group: "content", index: 1, element: {} as HTMLElement, accepts: ["text"] });
+  f.manager.registerSortable({ id: "invalid", group: "blocked", index: 0, element: {} as HTMLElement });
+  const source = { id: "child", type: "text" };
+  expect(f.instances[1]!.input.accept(source)).toBe(false);
+  expect(f.instances[2]!.input.accept(source)).toBe(true);
+  expect(f.instances[2]!.input.accept({ ...source, type: "image" })).toBe(false);
+  expect(f.instances[3]!.input.accept(source)).toBe(false);
+  f.manager.destroy();
+});
+
 test("empty drop zones use explicit locations for acceptance and commit", async () => {
   const commits: unknown[] = [];
   const f = fixture({ accept: (_ids, to) => to.group === "empty", onMoveIntent: intent => { commits.push(intent.to); } });