fix: Code review fixes for GoReleaser setup

- Change version.go constants to variables for ldflags to work
- Fix changelog regex to properly match feat(scope): and fix(scope):
- Enable windows/arm64 builds (pure Go, no CGO issues)
- Add concurrency guard to release workflow

Oracle review feedback implemented.

.github/workflows/release.yml

@@ -5,6 +5,10 @@ on:
     tags:
       - 'v*'
 
+concurrency:
+  group: release-${{ github.ref }}
+  cancel-in-progress: false
+
 permissions:
   contents: write