fix(maze-objects): 删掉 isOpenFloor 里恒真的 `|| true`

`hasFloor` 的内容检测写成 `(f.prop1 !== 0 || f.style !== 0 || f.sequence !== 0
|| true)`，末尾的 `|| true` 让整个条件恒为真：DS1 每个格子的每一层地板都有一条
记录，未绘制处是全零槽位，于是「没有地板美术的空格」也被判定为可放物件的地面。

删除 `|| true` 后，全零地板槽位不再算作地面；新增 6 个回归用例覆盖
painted / 全零 / 仅 style / 仅 sequence / hidden / 多层，以及「整关地板全为空槽
时不生成任何动态物件」。

TAG=agy
CONV=2a1934de-30ef-464e-b3f3-fcbcdbbc49f1

src/game/maze-objects.ts

@@ -234,8 +234,12 @@ export function isOpenFloor(cells: readonly (readonly Ds1Cell[])[], cx: number,
   const cell = row[cx]
   if (!cell) return false
 
-  // Must contain floor
-  const hasFloor = cell.floors.length > 0 && cell.floors.some(f => !f.hidden && (f.prop1 !== 0 || f.style !== 0 || f.sequence !== 0 || true))
+  // Must contain floor *art*. A `Ds1Floor` whose `prop1`, `style` and `sequence`
+  // are all zero is an empty slot, not a tile: DS1 stores one entry per floor
+  // layer for every cell, so a one-layer map has a zero-filled entry everywhere
+  // the level does not paint. The `|| true` that used to close this condition
+  // made the whole content test vacuous, so objects were placed on void cells.
+  const hasFloor = cell.floors.length > 0 && cell.floors.some(f => !f.hidden && (f.prop1 !== 0 || f.style !== 0 || f.sequence !== 0))
   if (!hasFloor) return false
 
   // Must not have a solid, visible wall

tests/maze-objects.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test } from 'vitest'
 import type { Ds1, Ds1Cell, Ds1Object } from '../src/formats/ds1.ts'
 import {
   populateDungeonObjects,
+  isOpenFloor,
   CANONICAL_SHRINES,
   CHEST_IDS_BY_ACT,
   RACK_IDS_BY_ACT,
@@ -482,3 +483,56 @@ describe('generateMaze end-to-end dynamic object integration', () => {
     expect(foundStatic).toBe(true)
   })
 })
+
+/**
+ * Regression cover for the `|| true` that used to close `isOpenFloor`'s content
+ * test (issue #58 item 2). With it, every `Ds1Floor` entry counted as floor art,
+ * so objects were seeded on cells the level never paints.
+ */
+describe('isOpenFloor content check', () => {
+  /** One cell grid with the given floor entries and no walls. */
+  function grid(floors: Ds1Cell['floors']): Ds1Cell[][] {
+    return [[{ walls: [], floors, shadows: [], substitutions: [] }]]
+  }
+
+  const painted = { prop1: 1, sequence: 0, style: 0, unknown1: 0, unknown2: 0, hidden: false }
+  const empty = { prop1: 0, sequence: 0, style: 0, unknown1: 0, unknown2: 0, hidden: false }
+
+  test('a painted floor cell is open floor', () => {
+    expect(isOpenFloor(grid([painted]), 0, 0)).toBe(true)
+  })
+
+  test('a cell whose only floor entry is all-zero is not open floor', () => {
+    expect(isOpenFloor(grid([empty]), 0, 0)).toBe(false)
+  })
+
+  test('style or sequence alone still counts as art', () => {
+    expect(isOpenFloor(grid([{ ...empty, style: 3 }]), 0, 0)).toBe(true)
+    expect(isOpenFloor(grid([{ ...empty, sequence: 7 }]), 0, 0)).toBe(true)
+  })
+
+  test('a hidden painted floor does not rescue an otherwise empty cell', () => {
+    expect(isOpenFloor(grid([{ ...painted, hidden: true }]), 0, 0)).toBe(false)
+  })
+
+  test('a multi-layer cell is open floor when any layer carries art', () => {
+    expect(isOpenFloor(grid([empty, painted]), 0, 0)).toBe(true)
+    expect(isOpenFloor(grid([empty, empty]), 0, 0)).toBe(false)
+  })
+
+  test('objects are not seeded into a level whose floors are all empty slots', () => {
+    const { level, rooms } = createSyntheticDungeon()
+    for (const row of level.cells) {
+      for (const cell of row) {
+        ;(cell.floors as Ds1Cell['floors'][number][]).splice(
+          0,
+          cell.floors.length,
+          { prop1: 0, sequence: 0, style: 0, unknown1: 0, unknown2: 0, hidden: false },
+        )
+      }
+    }
+    const result = populateDungeonObjects(rooms, 0, 0, level, 'Act 1 - Cave', 2, { density: 1.0 }, new Rng(7))
+    expect(result.placedObjects.length).toBe(0)
+  })
+})
+