feat(render): composite object tiles over a base tile (pipeline) + bigger cat

The black boxes around furniture/windows were transparent object tiles drawn
straight onto the dark canvas. Fix at the pipeline level, not as a tavern one-off:

- tileRenderer: a tile kind whose legend declares `over` (the ground it sits on)
  now draws that base tile FIRST, then the object on top — so the object's
  transparent areas show the floor/wall. Works for any scene, atlas or flat-colour
  fallback. Wall-grounding shadow strip now only applies to real walls, not objects.
- sceneModel TAVERN_LEGEND: declares over='floor' for bar/keg/shelf/table/chair/
  barrel/crate/rug and over='wall' for windows.
- catSprites: the cat occupies ~40% of its 50x50 frame, so scale to ~2x the cell
  and centre it — it now reads about tile-sized instead of tiny.

Client-only. Suite 57 suites / 413 tests green.

html/js/render/catSprites.js

@@ -27,9 +27,11 @@
         if (!im.complete || !im.naturalWidth) return false;
         var frame = Math.floor((now || 0) / FRAME_MS) % FRAMES;
         var sx = frame * FW;
-        var size = cell * 1.25;                       // a touch bigger than a tile
+        // The cat occupies only ~40% of its 50x50 frame (lots of transparent padding), so scale
+        // the frame to ~2x the cell and centre it — the visible cat then reads about tile-sized.
+        var size = cell * 2.0;
         var dx = e.x * cell + (cell - size) / 2;
-        var dy = e.y * cell + cell - size + cell * 0.12;
+        var dy = e.y * cell + (cell - size) / 2 + cell * 0.2;   // centred, nudged down onto the tile
         ctx.save();
         ctx.imageSmoothingEnabled = false;
         if (e.facing === 'left') {

html/js/render/sceneModel.js

@@ -7,19 +7,22 @@
     'use strict';
 
     // Tile kinds and how each renderer treats them (glyph for ASCII, colour for tiled/fancy).
+    // `over` names the ground tile an object sits on, so the renderer composites the object over it
+    // (its transparent areas show the floor/wall, not the dark canvas). Ground tiles (wall/floor/rug)
+    // have no `over` — they fill the cell.
     var TAVERN_LEGEND = {
         wall:   { char: '#', color: '#3a3f4b', solid: true },
-        window: { char: 'W', color: '#4a6a8a', solid: true },
+        window: { char: 'W', color: '#4a6a8a', solid: true,  over: 'wall' },
         floor:  { char: '·', color: '#6b4d33', solid: false },  // warm wood, not the old dark green
-        rug:    { char: '=', color: '#7a3b39', solid: false },
-        bar:    { char: '=', color: '#6a4a2a', solid: true },
-        keg:    { char: 'k', color: '#5a4028', solid: true },
-        shelf:  { char: 'h', color: '#4a3a28', solid: true },
-        table:  { char: 'T', color: '#6a4a2a', solid: true },
-        chair:  { char: 'c', color: '#5a4028', solid: false },  // walkable — stand on it to "sit"
-        barrel: { char: 'B', color: '#5a4028', solid: true },
-        crate:  { char: 'C', color: '#7a5a38', solid: true },
-        door:   { char: 'D', color: '#3fb950', solid: false }
+        rug:    { char: 'r', color: '#7a3b39', solid: false, over: 'floor' },
+        bar:    { char: '=', color: '#6a4a2a', solid: true,  over: 'floor' },
+        keg:    { char: 'k', color: '#5a4028', solid: true,  over: 'floor' },
+        shelf:  { char: 'h', color: '#4a3a28', solid: true,  over: 'floor' },
+        table:  { char: 'T', color: '#6a4a2a', solid: true,  over: 'floor' },
+        chair:  { char: 'c', color: '#5a4028', solid: false, over: 'floor' },  // walkable — stand on it to "sit"
+        barrel: { char: 'B', color: '#5a4028', solid: true,  over: 'floor' },
+        crate:  { char: 'C', color: '#7a5a38', solid: true,  over: 'floor' },
+        door:   { char: 'D', color: '#3fb950', solid: false, over: 'floor' }
     };
 
     // Layout character -> tile kind.

html/js/render/tileRenderer.js

@@ -107,9 +107,18 @@
                     var def = scene.legend[kind] || { color: '#333' };
                     var coord = useAtlas ? pickVariant(tmap[kind], x, y) : null;
                     if (coord) {
+                        // Object tiles (furniture, windows, torches, treasure…) are transparent
+                        // around the object. Legend `over` names the ground they sit on (floor/wall);
+                        // draw that first so the transparency shows the room, not the dark canvas.
+                        // Pipeline-level: any scene can declare it, not a tavern one-off.
+                        if (def.over && tmap[def.over]) {
+                            var base = pickVariant(tmap[def.over], x, y);
+                            if (base) atlas.draw(ctx, base[0], base[1], px, py, cell);
+                        }
                         atlas.draw(ctx, coord[0], coord[1], px, py, cell);
-                        // Dark bottom-edge strip grounds a solid wall against the floor below.
-                        if (def.solid) {
+                        // Dark bottom-edge strip grounds a solid WALL against the floor below (not
+                        // objects, which already sit on their own base tile).
+                        if (def.solid && !def.over) {
                             var strip = Math.max(2, cell * 0.16);
                             var sg = ctx.createLinearGradient(0, py + cell - strip, 0, py + cell);
                             sg.addColorStop(0, 'rgba(0,0,0,0)');
@@ -121,6 +130,10 @@
                         continue;
                     }
                     // Flat-colour fallback for any unmapped kind (or atlas not yet loaded).
+                    if (def.over && scene.legend[def.over]) {
+                        ctx.fillStyle = scene.legend[def.over].color;   // base colour under the object
+                        ctx.fillRect(px, py, cell, cell);
+                    }
                     ctx.fillStyle = def.color;
                     ctx.fillRect(px, py, cell, cell);
                     ctx.strokeStyle = 'rgba(0,0,0,0.25)';