Fix appendFonts plugin to use proper hooks

Author: IzumiSy

packages/core/vite.config.ts

@@ -1,4 +1,4 @@
-import { readFileSync, appendFileSync, existsSync } from "node:fs";
+import { readFileSync, existsSync } from "node:fs";
 import { resolve } from "node:path";
 import tsconfigPaths from "vite-tsconfig-paths";
 import react from "@vitejs/plugin-react";
@@ -9,21 +9,30 @@ import dts from "vite-plugin-dts";
 const whenProductionBuild = (mode: string) => mode === "production";
 
 /**
- * Appends the pre-generated fonts.generated.css to dist/app-shell.css
- * after Vite finishes bundling. This avoids Vite trying to resolve woff2
- * urls during build while still including fonts in the default styles export.
+ * Appends the pre-generated fonts.generated.css to the CSS bundle asset
+ * during generation. This avoids Vite trying to resolve woff2 urls during
+ * build while still including fonts in the default styles export.
+ *
+ * Using generateBundle (instead of closeBundle/writeBundle) ensures the file
+ * is written to disk only once, preventing spurious change-detection in
+ * downstream dev servers during watch mode.
  */
 function appendFonts(props: { appendCSSFile: string }): Plugin {
   return {
     name: "append-fonts",
-    closeBundle() {
+    enforce: "post",
+    generateBundle(_, bundle) {
       const fontsPath = resolve(import.meta.dirname, "src/assets/fonts.generated.css");
       if (!existsSync(fontsPath)) {
         this.error("src/assets/fonts.generated.css not found. Run `pnpm generate:fonts` first.");
       }
-      const dist = resolve(import.meta.dirname, "dist");
       const fontCss = readFileSync(fontsPath, "utf8");
-      appendFileSync(resolve(dist, props.appendCSSFile), "\n" + fontCss);
+      const cssAsset = Object.values(bundle).find(
+        (asset) => asset.type === "asset" && asset.fileName.endsWith(".css"),
+      );
+      if (cssAsset && cssAsset.type === "asset") {
+        cssAsset.source += "\n" + fontCss;
+      }
     },
   };
 }