fix(packages): add server-only bundles (#1349)

.github/scripts/bundle-size.js

@@ -163,6 +163,7 @@ async function measure(entryPoints, external = []) {
     write: false,
     outdir: '/tmp/bundle-size-out',
     external,
+    conditions: ['browser'],
     logLevel: 'silent',
   });
 
@@ -199,6 +200,7 @@ async function measureVirtual(code, resolveDir, external = []) {
     write: false,
     outdir: '/tmp/bundle-size-out',
     external,
+    conditions: ['browser'],
     logLevel: 'silent',
   });
 
@@ -213,12 +215,17 @@ async function measureVirtual(code, resolveDir, external = []) {
 }
 
 /**
- * Resolve the `default` condition from an export value.
- * Handles both `{ default: "./dist/..." }` objects and plain string values.
+ * Resolve the browser production path from an export value.
+ *
+ * Prefers `browser.default` (browser prod bundle) over top-level `default`
+ * (server bundle) so we measure the code consumers actually ship.
  */
 function resolveDefault(exportValue) {
   if (typeof exportValue === 'string') return exportValue;
   if (typeof exportValue === 'object' && exportValue !== null) {
+    if (typeof exportValue.browser === 'object' && exportValue.browser !== null) {
+      return exportValue.browser.default ?? exportValue.default ?? null;
+    }
     return exportValue.default ?? null;
   }
   return null;