Matches the platform used for baseline captures in ci.yml,
avoiding false diffs from font rendering differences.

https://claude.ai/code/session_01Bgey3hrVy9av1SHrpdo5bU

diff --git a/.github/workflows/preview.yml b/.github/workflows/preview.yml
index 68c3149..35f9b38 100644
--- a/.github/workflows/preview.yml
+++ b/.github/workflows/preview.yml
@@ -11,7 +11,7 @@ env:
 
 jobs:
   preview:
-    runs-on: ubuntu-latest
+    runs-on: macos-latest
     concurrency:
       group: pr-${{ github.event.number }}
     environment: