Feat: Host the NSA article's header image next to the article

Relative header_image paths (./img.webp) now resolve to /<slug>/img.webp, and article
assets also ship unhashed so og:image and JSON-LD URLs resolve.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

vite.config.js

@@ -1,9 +1,20 @@
 import { defineConfig } from "vite";
+import fs from "node:fs";
 import fg from "fast-glob";
 
+// Vite hashes images it finds in HTML into /assets/, but og:image and JSON-LD point at /<slug>/<file>, so ship those too
+const articleAssets = {
+  name: "article-assets",
+  generateBundle() {
+    for (const fileName of fg.sync("*/*", { cwd: "src", ignore: ["**/*.html"] }))
+      this.emitFile({ type: "asset", fileName, source: fs.readFileSync(`src/${fileName}`) });
+  }
+};
+
 export default defineConfig({
   root: "src",
   publicDir: "../public",
+  plugins: [articleAssets],
   build: {
     outDir: "../dist",
     emptyOutDir: true,