Merge origin/new-newnassets: new LPC rat assets and animations

Cherry-picked from new-newnassets (3 commits):
- bdf5a8d Add new start animation asset for game launch
- 5f2d09f Fix rat animations and restore map tiles
- 2e2c5bb feat: add LPC-style rat assets, sprite generation scripts, and grid extraction tools

Conflicts resolved:
- engine/sdl2.py: kept 'if scale:' wrapper (compatible, default scale=True)
- units/rat.py: kept animation frame computation (partial_move * 4)
- 12 PNG files (BMP_BABY/MALE/FEMALE_*): kept new-newnassets versions

Cleanup applied: removed ~480 working artifacts not appropriate for the
production repo:
- 25 PNG in repo root (male_rats*.png, spritesheet*.png)
- 416 tile extracts in tools/lpc_extract/grid/
- scattered debug PNGs (bushes, preview, montages, etc.)
- early iteration scripts (animate_rat v1-v4, restyle v2-v10, etc.)

Kept: 32 new LPC-style sprites in assets/Rat_LPC_Style/, 4 animation
sprite sheets in assets/Rat_Animated/, 64 updated Rat sprites, 22
final-version generator scripts, plus all .py/.md updates.

tools/lpc_extract/solve_grass.py

@@ -0,0 +1,22 @@
+from PIL import Image
+
+src_img = Image.open('/home/enne2/dev/asset-maker/assets/poses/sources/lpc-revised/Terrain/terrain_spring.png').convert('RGBA')
+
+# The plain grass tile in LPC terrain is typically at col 4, row 1 (0-indexed)
+tx, ty = 4, 1
+box = (tx * 32, ty * 32, (tx + 1) * 32, (ty + 1) * 32)
+tile32 = src_img.crop(box)
+
+# Strategy 1: Tile it 2x2 to make a 64x64 image
+img_tiled = Image.new('RGBA', (64, 64))
+img_tiled.paste(tile32, (0, 0))
+img_tiled.paste(tile32, (32, 0))
+img_tiled.paste(tile32, (0, 32))
+img_tiled.paste(tile32, (32, 32))
+img_tiled.save('/home/enne2/dev/mice/tools/lpc_extract/BMP_1_GRASS_1_tiled.png')
+
+# Strategy 2: Scale it 2x to make a 64x64 image
+img_scaled = tile32.resize((64, 64), Image.NEAREST)
+img_scaled.save('/home/enne2/dev/mice/tools/lpc_extract/BMP_1_GRASS_1_scaled.png')
+
+print("Created BMP_1_GRASS_1_tiled.png and BMP_1_GRASS_1_scaled.png")