fix: skip arch annotation on sources that already have one

The sed command was corrupting microsoft-prod.list which already has
[arch=...] annotations, producing malformed double-bracket entries.
Only modify lines without an existing arch spec.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: userFRM

.github/workflows/release.yml

@@ -45,7 +45,7 @@ jobs:
         if: matrix.cross
         run: |
           sudo dpkg --add-architecture arm64
-          sudo sed -i 's/^deb /deb [arch=amd64] /' /etc/apt/sources.list.d/*.list
+          sudo sed -i '/\[arch=/!s/^deb /deb [arch=amd64] /' /etc/apt/sources.list.d/*.list 2>/dev/null || true
           echo "deb [arch=arm64] http://ports.ubuntu.com/ $(lsb_release -cs) main restricted universe" | sudo tee /etc/apt/sources.list.d/arm64.list
           echo "deb [arch=arm64] http://ports.ubuntu.com/ $(lsb_release -cs)-updates main restricted universe" | sudo tee -a /etc/apt/sources.list.d/arm64.list
           sudo apt-get update