feat: author first playable mystery

src/boardDomain.test.ts

@@ -7,6 +7,7 @@ import {
   containedIds,
   folderIsOpen,
   moveBoardPoint,
+  nextOpenBoardPosition,
   normalizeCase,
   panViewport,
   relationPosition,
@@ -58,6 +59,16 @@ describe('board coordinate math', () => {
     expect(zoomFromWheel(1, 10_000)).toBe(MIN_BOARD_ZOOM)
     expect(zoomFromWheel(1, -10_000)).toBe(MAX_BOARD_ZOOM)
   })
+
+  it('places new exhibits in deterministic open slots', () => {
+    const preferred = { x: 500, y: 400 }
+    expect(nextOpenBoardPosition([], preferred, { width: 280 })).toEqual(preferred)
+    expect(nextOpenBoardPosition([{ x: 500, y: 400, width: 280 }], preferred, { width: 280 })).toEqual({ x: 826, y: 400 })
+    expect(nextOpenBoardPosition([
+      { x: 500, y: 400, width: 280 },
+      { x: 826, y: 400, width: 280 },
+    ], preferred, { width: 280 })).toEqual({ x: 174, y: 400 })
+  })
 })
 
 describe('timeline projection', () => {