docs(design): remove SVG, use PNG logo only

SVG icon is no longer in use. public/logo.png (1024x1024 RGBA) is
the single logo asset. DESIGN.md updated accordingly: SVG snippet
removed, wordmark pattern and <head> references updated to PNG.

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

node_modules/dlv/index.js

@@ -0,0 +1,7 @@
+export default function dlv(obj, key, def, p, undef) {
+	key = key.split ? key.split('.') : key;
+	for (p = 0; p < key.length; p++) {
+		obj = obj ? obj[key[p]] : undef;
+	}
+	return obj === undef ? def : obj;
+}