Rework Gothic hall as a stone nave interior.

Add gothic ashlar/vault/floor textures, compound piers with transverse ribs, proper lancet arches, textured door-flanking panels, and lightScale for shaft-lit naves. Docs updated in basics and data-and-images.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/components/GalleryWindows.tsx

@@ -69,10 +69,56 @@ function WindowFrame({
       </mesh>
 
       {arch && style === 'gothic-lancet' && (
-        <mesh position={[0, height / 2 + 0.15, -depth / 2 + 0.02]}>
-          <coneGeometry args={[width / 2 + frameW, 0.5, 4]} />
-          <meshStandardMaterial color={trimColor} roughness={0.4} metalness={0.35} />
-        </mesh>
+        <>
+          {/* Two-centred arch head built from short chords */}
+          {Array.from({ length: 14 }, (_, i) => {
+            const segs = 14;
+            const rise = width * 0.62;
+            const pt = (t: number): [number, number] => {
+              const x = (t - 0.5) * (width + frameW * 2);
+              const y = Math.pow(Math.cos((t - 0.5) * Math.PI), 0.72) * rise;
+              return [x, y];
+            };
+            const [x0, y0] = pt(i / segs);
+            const [x1, y1] = pt((i + 1) / segs);
+            const len = Math.hypot(x1 - x0, y1 - y0);
+            return (
+              <mesh
+                key={i}
+                position={[(x0 + x1) / 2, height / 2 + (y0 + y1) / 2, -depth / 2 + 0.02]}
+                rotation={[0, 0, Math.atan2(y1 - y0, x1 - x0)]}
+              >
+                <boxGeometry args={[len * 1.15, frameW * 1.4, depth]} />
+                <meshStandardMaterial color={trimColor} roughness={0.55} metalness={0.15} />
+              </mesh>
+            );
+          })}
+          {/* Glazed spandrel filling the arch head */}
+          <mesh position={[0, height / 2 + width * 0.16, 0.01]}>
+            <planeGeometry args={[width * 0.72, width * 0.5]} />
+            <meshStandardMaterial
+              color="#9fc4ef"
+              emissive="#9fc4ef"
+              emissiveIntensity={0.6}
+              toneMapped={false}
+              transparent
+              opacity={0.8}
+            />
+          </mesh>
+          {/* Mullions and transoms */}
+          {[-width / 4, width / 4].map((ox) => (
+            <mesh key={ox} position={[ox, 0, -depth / 2 + 0.03]}>
+              <boxGeometry args={[0.045, height, depth]} />
+              <meshStandardMaterial color={trimColor} roughness={0.55} metalness={0.15} />
+            </mesh>
+          ))}
+          {[height / 3, -height / 6].map((oy) => (
+            <mesh key={oy} position={[0, oy, -depth / 2 + 0.03]}>
+              <boxGeometry args={[width, 0.035, depth]} />
+              <meshStandardMaterial color={trimColor} roughness={0.55} metalness={0.15} />
+            </mesh>
+          ))}
+        </>
       )}
 
       {style === 'roman-arch' && (