Pin macOS Swift action to arm64

Author: navjack

.github/workflows/macos-package-build.yml

@@ -19,6 +19,7 @@ jobs:
         with:
           swift-version: swift-6.3-branch
           swift-build: 6.3-DEVELOPMENT-SNAPSHOT-2026-02-27-a
+          build_arch: arm64
 
       - name: Verify Swift Toolchain
         run: swift --version

SCRATCHPAD.md

@@ -115,3 +115,4 @@
 - `main` now also has a dedicated macOS packaging workflow so GitHub can produce fresh app/CLI zips on each `main` push; future public releases can pull both Win64 and macOS artifacts directly from Actions.
 - The first macOS Actions run failed because `macos-14` defaulted to Swift 5.10; the workflow now bootstraps the same Swift 6.3 snapshot family used by the Windows lane before packaging.
 - The second macOS Actions run exposed stricter Swift 6.3 actor-isolation checks in the native SwiftUI layer; the affected editor/game root views are now explicitly `@MainActor`, matching the `@MainActor` stores/controllers they observe.
+- The macOS workflow now explicitly pins `gha-setup-swift` to `build_arch: arm64`; relying on the action default (`amd64`) on `macos-14` was the wrong assumption and makes the runner setup ambiguous.