Complete the overworld foundation

Port forced movement (turn delays, bumps, ice, currents, pits), dynamic
return warps, elevators, Surf, Cut, Strength and cycling rules, working
map blocks with changeblock/changemapblocks, and the remaining NPC
movement types and movement commands.

Add tileset animation from the ROM's command tables, grass sprite
priority and special map palettes; room decorations with ownership, the
bedroom PC and save migration; and Key Items access to the Bicycle.

Fourteen original-engine traces compare positions, facing, actors, event
flags and scripted poses. Tile animation matches original VRAM for four
tilesets, and LoadMapPals matches 192 palette cases. skyfall_top now
keeps the $60 sprite offset its step function leaves behind.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/game/rendering/pixels.ts

@@ -10,7 +10,15 @@ export function drawTile(
   x: number,
   y: number,
   palette: Palette,
-  options: { transparent?: boolean; flipX?: boolean; flipY?: boolean } = {},
+  options: {
+    transparent?: boolean;
+    flipX?: boolean;
+    flipY?: boolean;
+    /** Background color indices per pixel: a background tile records them;
+     * an OAM_PRIO sprite (`behind`) only draws over color 0. */
+    indices?: Uint8Array;
+    behind?: boolean;
+  } = {},
 ) {
   const offset = tile * 16;
   if (offset < 0 || offset + 16 > graphics.length) return;
@@ -25,6 +33,11 @@ export function drawTile(
       const px = x + col,
         py = y + row;
       if (px < 0 || py < 0 || px >= width || py >= height) continue;
+      if (options.indices) {
+        if (options.behind) {
+          if (options.indices[py * width + px]) continue;
+        } else if (!options.transparent) options.indices[py * width + px] = index;
+      }
       const destination = (py * width + px) * 4,
         color = palette[index];
       target[destination] = color[0];