fix: remove musl target - no ONNX Runtime support

Even x86_64-unknown-linux-musl doesn't have ONNX Runtime binaries.
Focus on native builds only:
- Linux x86_64 (gnu)
- Windows x86_64 (msvc/gnu) and aarch64
- macOS x86_64 and aarch64

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: runonthespot

.github/workflows/release.yml

@@ -57,11 +57,6 @@ jobs:
             target: x86_64-unknown-linux-gnu
             use-cross: false
 
-          - build: linux-x86_64-musl
-            os: ubuntu-latest
-            target: x86_64-unknown-linux-musl
-            use-cross: true
-          
 
           # macOS builds
           - build: macos-x86_64

Cross.toml

@@ -1,5 +1 @@
-# Use sccache's proven Docker images with pkg-config pre-build
-[target.x86_64-unknown-linux-musl]
-image = "messense/rust-musl-cross:x86_64-musl"
-pre-build = ["apt-get update && apt-get install -y pkg-config libssl-dev"]
-
+# Cross-compilation configuration (currently empty - no cross targets)