fix: standardize inline script transpilation in tsup config

Use stdin-based esbuild.build with proper TS transpilation, minification,
and ESM output format matching v5's proven inline-script-loader pattern.

tsup.config.ts

@@ -1,4 +1,78 @@
 import { defineConfig } from "tsup";
+import type { Plugin } from "esbuild";
+import path from "path";
+
+/**
+ * Esbuild plugin that bundles `.inline.ts` files into browser-ready JavaScript strings.
+ *
+ * Problem: Inline scripts are embedded as raw text into `<script>` tags in the browser.
+ * The previous text-loader read `.inline.ts` files verbatim, meaning TypeScript syntax
+ * (type annotations, `as` casts, non-null assertions, interfaces) survived into the
+ * browser and caused parse errors.
+ *
+ * Solution: Use `esbuild.build()` to transpile TypeScript and bundle local/npm imports
+ * into a single self-contained script. The result is returned as a text string that can
+ * be safely injected into a `<script>` tag.
+ *
+ * This mirrors Quartz v5's own `inline-script-loader` in `quartz/cli/handlers.js`.
+ */
+const inlineScriptPlugin: Plugin = {
+  name: "inline-script-loader",
+  setup(parentBuild) {
+    const absWorkingDir = parentBuild.initialOptions.absWorkingDir ?? process.cwd();
+
+    // SCSS files are loaded as raw text (CSS injected via style tags)
+    parentBuild.onLoad({ filter: /\.scss$/ }, async (args) => {
+      const fs = await import("fs");
+      const text = await fs.promises.readFile(args.path, "utf8");
+      return {
+        contents: text,
+        loader: "text",
+      };
+    });
+
+    // Inline TypeScript files are transpiled + bundled for the browser
+    parentBuild.onLoad({ filter: /\.inline\.ts$/ }, async (args) => {
+      const esbuild = await import("esbuild");
+      const fs = await import("fs");
+      let text = await fs.promises.readFile(args.path, "utf8");
+
+      // Strip export statements that were added for the module system —
+      // inline scripts run in a <script> tag, not as ES modules
+      text = text.replace(/^export default /gm, "");
+      text = text.replace(/^export /gm, "");
+
+      const resolveDir = path.dirname(args.path);
+      const sourcefile = path.relative(absWorkingDir, args.path);
+
+      const result = await esbuild.build({
+        stdin: {
+          contents: text,
+          loader: "ts",
+          resolveDir,
+          sourcefile,
+        },
+        write: false,
+        bundle: true,
+        minify: true,
+        platform: "browser",
+        format: "esm",
+        target: "es2020",
+        sourcemap: false,
+        // Preserve dynamic CDN imports (e.g. graph plugin loading d3/pixi from CDN)
+        external: ["http://*", "https://*"],
+      });
+
+      const js = result.outputFiles?.[0]?.text;
+      if (!js) throw new Error(`inline-script-loader: no JS output for ${args.path}`);
+
+      return {
+        contents: js,
+        loader: "text",
+      };
+    });
+  },
+};
 
 export default defineConfig({
   entry: {
@@ -18,28 +92,5 @@ export default defineConfig({
     options.jsx = "automatic";
     options.jsxImportSource = "preact";
   },
-  esbuildPlugins: [
-    {
-      name: "text-loader",
-      setup(build) {
-        build.onLoad({ filter: /\.scss$/ }, async (args) => {
-          const fs = await import("fs");
-          const text = await fs.promises.readFile(args.path, "utf8");
-          return {
-            contents: text,
-            loader: "text",
-          };
-        });
-
-        build.onLoad({ filter: /\.inline\.ts$/ }, async (args) => {
-          const fs = await import("fs");
-          const text = await fs.promises.readFile(args.path, "utf8");
-          return {
-            contents: text,
-            loader: "text",
-          };
-        });
-      },
-    },
-  ],
+  esbuildPlugins: [inlineScriptPlugin],
 });