Fix Namespace macOS runner shape

evolution/proposals/BEP-0009-release-infrastructure-and-store-upload-pipeline.md

@@ -107,6 +107,9 @@ The same change also makes the forge itself the release authority: release tags
   workflow so stale generic Namespace jobs cannot consume Apple release runners:
   - `namespace-profile-linux-medium-apple`
   - `namespace-profile-macos-large-apple`
+- Configure macOS Namespace targets with the Compute API CPU-by-memory shape
+  format. `12x28` is the Burrow large macOS baseline; platform-prefixed values
+  such as `macos/arm64:8x16` are not accepted by the macOS launcher.
 - Run forge Namespace services with the repo-owned `nsc` package and keep it
   current with the token format expected by Namespace. `nsc 0.0.520` is the
   first required baseline for revokable token-file auth.