Add comment explaining use of tsc.

Author: taeold

tsconfig.release.json

@@ -1,4 +1,7 @@
 {
+  // This config is used by `tsc` to generate .d.ts files only.
+  // tsdown handles CJS/ESM transpilation but has dts generation issues,
+  // so we use tsc for type declarations. See tsdown.config.mts for details.
   "compilerOptions": {
     "declaration": true,
     "emitDeclarationOnly": true,

tsdown.config.mts

@@ -10,14 +10,17 @@ const rewriteProtoPathMjs = {
   },
 };
 
+// Note: We use tsc (via tsconfig.release.json) for .d.ts generation instead of tsdown's
+// built-in dts option due to issues with rolldown-plugin-dts.
+// See: https://github.com/sxzz/rolldown-plugin-dts/issues/121
 export default defineConfig([
   {
     entry: "src/**/*.ts",
     unbundle: true,
     format: "cjs",
     outDir: "lib",
     clean: true,
-    dts: false,
+    dts: false, // Use tsc for type declarations
     treeshake: false,
     external: ["../../../protos/compiledFirestore"],
   },
@@ -27,7 +30,7 @@ export default defineConfig([
     format: "esm",
     outDir: "lib/esm",
     clean: false, // Don't clean - need to keep cjs/ output
-    dts: false,
+    dts: false, // Use tsc for type declarations
     treeshake: false,
     plugins: [rewriteProtoPathMjs],
   },