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/@nodelib/fs.walk/out/readers/reader.d.ts

@@ -0,0 +1,6 @@
+import type Settings from '../settings';
+export default class Reader {
+    protected readonly _root: string;
+    protected readonly _settings: Settings;
+    constructor(_root: string, _settings: Settings);
+}