feat(engine): Tiled P3 — animated tiles (deterministic frame clock) + tile objects (#71)

- Animated tiles: a tileset <animation>'s {tileid, duration} frames advance as a
  pure function of the fixed 60/s engine frame counter (the same clock SpriteAnim
  rides), so an animated GID resolves at draw to the current frame's GID with its
  flip flags preserved — deterministic, frame-identical across runs, ticks for
  free. Tiled.frame_gid(map, gid, frame) / Tiled.animated(map, gid) expose it;
  Tiled.draw_anim(map, camx, camy, frame) draws a map with animations advanced.
- Tile objects: object-layer entries with a `gid` draw the tile image (with their
  own flip flags), bottom-anchored at the object position, as placeable sprites;
  tmap_draw_full now renders object layers alongside tile layers.

Proven by library/tiled_p3.ludic (14 assertions): frame advance at authored
durations + wrap, flip flags riding an animation swap, tile-object parse + draw +
flip mirroring, and the design's named rpg/beach_tileset.tsx (33 <animation>
blocks / 131 frames). x test: 94 passed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/tiled-fixtures/anim_tiles.tsx

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Hand-authored animated tileset over the Kenney atlas (issue #71). CC0. -->
+<tileset version="1.10" tiledversion="1.10.2" name="anim" tilewidth="16" tileheight="16" spacing="1" tilecount="132" columns="12">
+ <image source="../kenney/tiny-dungeon/Tilemap/tilemap.png" width="203" height="186"/>
+ <tile id="0">
+  <animation>
+   <frame tileid="0" duration="100"/>
+   <frame tileid="40" duration="100"/>
+   <frame tileid="80" duration="100"/>
+  </animation>
+ </tile>
+</tileset>