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/postcss-js/async.js

@@ -0,0 +1,15 @@
+let postcss = require('postcss')
+
+let parse = require('./parser')
+let processResult = require('./process-result')
+
+module.exports = function async(plugins) {
+  let processor = postcss(plugins)
+  return async input => {
+    let result = await processor.process(input, {
+      parser: parse,
+      from: undefined
+    })
+    return processResult(result)
+  }
+}