feat: switch to LPC tileset with layered autotiling

Replace the 16x16 tileset with LPC Base Assets (32x32 tiles, 1.5x scale).
Uses a 4-layer rendering approach:
- Layer 0: solid grass base (grass.png)
- Layer 1: water transitions (watergrass.png) with LPC autotile edges
- Layer 2: dirt transitions (dirt.png) with LPC autotile edges
- Layer 3: tree canopy decorations (treetop.png)

LPC autotile format: 3x6 grid with inner/outer corners, edges, and fill
tiles. Edge tiles are selected based on 8-neighbor terrain analysis.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/map/mapGenerator.ts

@@ -108,12 +108,11 @@ export function generateMap(
   }
 
   // --- Trees (decorations on grass tiles) ---
-  // Tree tile indices in the tileset (17 cols wide):
-  //   Deciduous tree top:  row 2, col 9  = 2*17+9  = 43  (but multi-tile)
-  //   Small bush:          row 7, col 9  = 7*17+9  = 128
-  //   Pine tree:           row 3, col 15 = 3*17+15 = 66
-  // We'll use a few different tree/bush decoration tiles
-  const TREE_TILES = [128, 129, 130, 145, 146]; // small plants/bushes from right side of tileset
+  // Tree tile indices reference treetop.png (6 cols x 7 rows)
+  // Pick recognizable canopy center tiles from each of the 4 trees:
+  //   Deciduous 1 center: (1,1) = 7    Deciduous 2 center: (4,1) = 10
+  //   Conifer 1 center:   (1,5) = 31   Conifer 2 center:   (4,5) = 34
+  const TREE_TILES = [7, 10, 31, 34];
 
   for (let y = 1; y < height - 1; y++) {
     for (let x = 1; x < width - 1; x++) {