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/fastq/example.mjs

@@ -0,0 +1,9 @@
+import { promise as queueAsPromised } from './queue.js'
+
+const queue = queueAsPromised(worker, 1)
+
+console.log('the result is', await queue.push(42))
+
+async function worker (arg) {
+  return 42 * 2
+}