Port Docs-Viewer to slatehtml as the docs-viewer package.

Replace the classic DOM shell with slate widgets, markdown→slate rendering, and a CI index build that uses build-docs.cjs.

vite.config.js

@@ -0,0 +1,62 @@
+import { defineConfig } from "vite";
+import { createRequire } from "node:module";
+import { cpSync, existsSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { umc } from "slatehtml/umc/vite";
+
+const require = createRequire(import.meta.url);
+const here = dirname(fileURLToPath(import.meta.url));
+const uiSrc = join(dirname(require.resolve("slatehtml-ui/package.json")), "src");
+const docsSrc = join(here, "src");
+
+function copyDocsStatic() {
+  const paths = ["index.json", "docs", "img", "example.index.json"];
+  return {
+    name: "copy-docs-static",
+    writeBundle(outputOptions) {
+      const outDir = outputOptions.dir || join(here, "dist");
+      for (const name of paths) {
+        const from = join(here, name);
+        if (!existsSync(from)) continue;
+        cpSync(from, join(outDir, name), { recursive: true });
+      }
+    },
+  };
+}
+
+export default defineConfig({
+  root: here,
+  base: "./",
+  plugins: [umc({ roots: [uiSrc, docsSrc] }), copyDocsStatic()],
+  server: {
+    fs: {
+      allow: [here, join(here, "..", "slatehtml")],
+    },
+  },
+  build: {
+    target: "es2022",
+    outDir: "dist",
+    emptyOutDir: true,
+  },
+  resolve: {
+    alias: [
+      {
+        find: "slatehtml-ui/configure",
+        replacement: join(uiSrc, "configure.js"),
+      },
+      {
+        find: "slatehtml-ui/icons/fontawesome",
+        replacement: join(uiSrc, "fontawesome-icons.js"),
+      },
+      {
+        find: "slatehtml-ui/icons/lucide",
+        replacement: join(uiSrc, "lucide-icons.js"),
+      },
+      {
+        find: "docs-viewer/prose.css",
+        replacement: join(docsSrc, "prose.css"),
+      },
+    ],
+  },
+});