feat: 在 Act 场景中挂载 GameEngine 提供真实的模拟物理状态

将刚才提取出的引擎初始化进 `act-scene.ts`，配置一个空的怪物列表。
使得 Act 地图不再仅仅是个“游览器”，而是拥有血条、法力、体力、碰撞并进行 ticks 的真实服务器沙盒对象。

src/scene/act-scene.ts

@@ -31,6 +31,8 @@ import {
 } from '../game/d2map.ts'
 import type { CollisionGrid } from '../game/d2map.ts'
 import { depthInsertIndex } from '../game/map.ts'
+import { GameEngine, syncEngineState } from "../game/engine.ts"
+import { DEMO_MONSTERS, DEMO_EXPERIENCE, DEMO_BASES, DEMO_AFFIXES, DEMO_SKILLS, DEMO_NPCS, DEMO_QUESTS } from "../game/demo-data.ts"
 import { buildAtlas } from '../render/atlas.ts'
 import type { AtlasFrame, SpriteAtlas } from '../render/atlas.ts'
 import { SpriteRenderer } from '../render/renderer.ts'
@@ -702,7 +704,6 @@ function runScene(runtime: MapRuntime, renderer: SpriteRenderer, started: number
   const actSelect = document.querySelector<HTMLSelectElement>('#act')!
   const variantSelect = document.querySelector<HTMLSelectElement>('#variant')!
 
-  const player = { x: runtime.spawn.x, y: runtime.spawn.y, facing: 0, walkFrame: 0, moving: false }
   const input = new KeyboardInput()
   input.attach()
   let skippedDraws = 0
@@ -711,34 +712,76 @@ function runScene(runtime: MapRuntime, renderer: SpriteRenderer, started: number
   const camera = new ViewportCamera(canvas, runtime.widthPx, runtime.heightPx)
   camera.attach()
 
+
+  let playerMoving = false
+  let playerWalkFrame = 0
+  const engine = new GameEngine(
+    {
+      widthPx: runtime.widthPx,
+      heightPx: runtime.heightPx,
+      overlap: (x, y) => (collides(runtime.grid, x, y) ? 1 : 0),
+    },
+    {
+      spawn: runtime.spawn,
+      stats: [],
+      xpTable: DEMO_EXPERIENCE,
+      itemBases: DEMO_BASES,
+      prefixAffixes: DEMO_AFFIXES,
+      suffixAffixes: DEMO_AFFIXES,
+      skills: DEMO_SKILLS,
+      npcDefs: DEMO_NPCS,
+      questDefs: DEMO_QUESTS,
+      combatOptions: {
+        playerSpeed: WALK_SPEED,
+        playerReach: 52,
+        playerCooldownTicks: 12,
+        playerDamage: 7,
+        playerManaPerAttack: 2,
+        respawnTicks: 75,
+      },
+      lootSeed: 0x5eed,
+      talkRadius: 80,
+      pickupRadius: 64,
+      inventoryCols: 10,
+      inventoryRows: 4,
+    }
+  )
+
   const loop = new GameLoop({
     tickRate: 25,
     onTick: () => {
+      engine.tick({
+        movement: input.movement(),
+        attacking: input.attacking,
+        pickingUp: input.pickingUp,
+        talking: input.talking,
+        digits: input.digits,
+        saving: input.saving,
+        loading: input.loading,
+      })
+
+      const player = engine.world.player
       const movement = input.movement()
-      player.moving = movement.x !== 0 || movement.y !== 0
-      if (player.moving) {
-        // Input is screen-space: the diamond lattice is rotated 45° from the
-        // screen axes, so "north" walks along a cell diagonal.
-        const length = Math.hypot(movement.x, movement.y)
-        const step = (WALK_SPEED / 25) / length
-        if (!collides(runtime.grid, player.x + movement.x * step, player.y)) player.x += movement.x * step
-        if (!collides(runtime.grid, player.x, player.y + movement.y * step)) player.y += movement.y * step
-        player.facing = facingOf(movement.x, movement.y)
-        player.walkFrame = (player.walkFrame + 1) % 24
+      let playerMoving = movement.x !== 0 || movement.y !== 0
+      if (playerMoving) {
+        playerWalkFrame = (playerWalkFrame + 1) % 24
       } else {
-        player.walkFrame = 0
+        playerWalkFrame = 0
       }
-      state.tick = loop.tick
+
+      state.tick = engine.world.tick
       state.x = player.x
       state.y = player.y
       state.facing = player.facing
+
+      syncEngineState(engine, state)
     },
     onRender: () => {
       if (state.pagesAtFirstFrame < 0) {
         state.pagesAtFirstFrame = runtime.pages.filter(page => page !== null).length
         state.firstFrameMs = Math.round(performance.now() - started)
       }
-      renderer.begin({ x: player.x, y: player.y - 16, zoom: camera.zoom }, [0.03, 0.03, 0.04])
+      renderer.begin({ x: engine.world.player.x, y: engine.world.player.y - 16, zoom: camera.zoom }, [0.03, 0.03, 0.04])
       skippedDraws = 0
       const drawTiles = (list: readonly Drawable[], from: number, to: number): void => {
         for (let index = from; index < to; index += 1) {
@@ -749,7 +792,7 @@ function runScene(runtime: MapRuntime, renderer: SpriteRenderer, started: number
         }
       }
       drawTiles(runtime.floors, 0, runtime.floors.length)
-      const cell = cellOf(runtime.grid, player.x, player.y)
+      const cell = cellOf(runtime.grid, engine.world.player.x, engine.world.player.y)
       const playerDepth = cell.x + cell.y
 
       let wallIdx = 0
@@ -790,20 +833,20 @@ function runScene(runtime: MapRuntime, renderer: SpriteRenderer, started: number
       drawUpToDepth(playerDepth)
       if (character === null) {
         // Placeholder until the character archive has been read.
-        renderer.drawSolid(player.x - MARKER_WIDTH / 2, player.y - MARKER_HEIGHT, MARKER_WIDTH, MARKER_HEIGHT, [0.85, 0.75, 0.45, 1])
-        renderer.drawSolid(player.x - MARKER_WIDTH / 2, player.y - 6, MARKER_WIDTH, 6, [0.35, 0.25, 0.15, 1])
+        renderer.drawSolid(engine.world.player.x - MARKER_WIDTH / 2, engine.world.player.y - MARKER_HEIGHT, MARKER_WIDTH, MARKER_HEIGHT, [0.85, 0.75, 0.45, 1])
+        renderer.drawSolid(engine.world.player.x - MARKER_WIDTH / 2, engine.world.player.y - 6, MARKER_WIDTH, 6, [0.35, 0.25, 0.15, 1])
       } else {
-        const direction = facingToDirection(player.facing, character.directions)
-        const groupIndex = (player.moving ? character.walk : character.stand) + direction
+        const direction = facingToDirection(engine.world.player.facing, character.directions)
+        const groupIndex = (playerMoving ? character.walk : character.stand) + direction
         const group = character.groups[groupIndex] ?? character.groups[character.walk + direction]
-        const frameIndex = player.moving
-          ? Math.floor(player.walkFrame / 3) % Math.max(1, group?.length ?? 1)
+        const frameIndex = playerMoving
+          ? Math.floor(playerWalkFrame / 3) % Math.max(1, group?.length ?? 1)
           : 0
         const frame = group?.[frameIndex]
         if (frame !== undefined) {
-          // Feet at the player's position: the composited frame is anchored by its
+          // Feet at the engine.world.player's position: the composited frame is anchored by its
           // bottom edge, which is where the COF puts the sprite's origin.
-          renderer.draw(frame, player.x - frame.width / 2, player.y - frame.height + FEET_HEIGHT / 2, { atlas: character.handle })
+          renderer.draw(frame, engine.world.player.x - frame.width / 2, engine.world.player.y - frame.height + FEET_HEIGHT / 2, { atlas: character.handle })
           state.characterFrames += 1
           state.characterGroup = groupIndex
         }
@@ -823,7 +866,7 @@ function runScene(runtime: MapRuntime, renderer: SpriteRenderer, started: number
       hud.textContent = `${runtime.level} · ${runtime.quadrant} · ${runtime.source === 'pack' ? '资源包' : '读归档'}`
         + ` · ${String(runtime.cellsX)}×${String(runtime.cellsY)} 格 · ${String(runtime.floors.length)} 地面 / ${String(runtime.walls.length)} 墙`
         + ` · 页 ${String(state.pagesLoaded)}/${String(state.pagesTotal)}`
-        + ` · 对象 ${String(runtime.objects)} · ${loop.tickRate.toFixed(1)} tps · pos ${player.x.toFixed(0)},${player.y.toFixed(0)}`
+        + ` · 对象 ${String(runtime.objects)} · ${loop.tickRate.toFixed(1)} tps · pos ${engine.world.player.x.toFixed(0)},${engine.world.player.y.toFixed(0)}`
         + (skippedDraws > 0 ? ` · 待页 ${String(skippedDraws)}` : '')
     },
   })