Consolidate arm64 and aarch64 naming to aarch64

ARM's 64-bit architecture is officially called AArch64. Apple calls it
"arm64" on macOS, but they're the same instruction set. Using aarch64
consistently makes the directory structure clearer.

Changes:
- Renamed build-osx-arm64 to build-osx-aarch64
- Changed ARCH_NAME from arm64 to aarch64 for Darwin build
- Updated release job dependencies

New directory structure:
  ./static
  ├── aarch64
  │   ├── Darwin
  │   │   └── libasyncprocess.a
  │   └── Linux
  │       └── libasyncprocess.a
  └── x86_64
      ├── Darwin
      │   └── libasyncprocess.a
      └── Linux
          └── libasyncprocess.a

Author: Claude

.github/workflows/build.yml

@@ -97,15 +97,15 @@ jobs:
         name: ${{ env.RESULT_NAME }}
         path: ${{ env.RESULT_PATH }}
 
-  build-osx-arm64:
-    runs-on: macos-14  # macOS 14 runs on Apple Silicon (arm64)
+  build-osx-aarch64:
+    runs-on: macos-14  # macOS 14 runs on Apple Silicon (aarch64/arm64)
     timeout-minutes: 90
     env:
       OS_NAME: Darwin
-      ARCH_NAME: arm64
+      ARCH_NAME: aarch64
       LIB_NAME: libasyncprocess.a
-      RESULT_NAME: result-osx-arm64
-      RESULT_PATH: result-osx-arm64
+      RESULT_NAME: result-osx-aarch64
+      RESULT_PATH: result-osx-aarch64
       RESULT_PATH_SUB: result-async/static
     steps:
     - uses: actions/checkout@v4
@@ -189,7 +189,7 @@ jobs:
 
   release:
     runs-on: ubuntu-latest
-    needs: [build-linux-x86_64, build-linux-aarch64, build-osx-arm64, build-osx-x86_64]
+    needs: [build-linux-x86_64, build-linux-aarch64, build-osx-aarch64, build-osx-x86_64]
     if: startsWith(github.ref, 'refs/tags/')
     steps:
     - name: Download all artifacts