feat(release): add SDK release types and config converter

Add SDKRelease struct to hold SDK release results and toSDKConfig
helper function to convert release.SDKConfig to sdk.Config.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/release/sdk.go

@@ -0,0 +1,36 @@
+// Package release provides release automation with changelog generation and publishing.
+package release
+
+import (
+	"github.com/host-uk/core/pkg/sdk"
+)
+
+// SDKRelease holds the result of an SDK release.
+type SDKRelease struct {
+	// Version is the SDK version.
+	Version string
+	// Languages that were generated.
+	Languages []string
+	// Output directory.
+	Output string
+}
+
+// toSDKConfig converts release.SDKConfig to sdk.Config.
+func toSDKConfig(cfg *SDKConfig) *sdk.Config {
+	if cfg == nil {
+		return nil
+	}
+	return &sdk.Config{
+		Spec:      cfg.Spec,
+		Languages: cfg.Languages,
+		Output:    cfg.Output,
+		Package: sdk.PackageConfig{
+			Name:    cfg.Package.Name,
+			Version: cfg.Package.Version,
+		},
+		Diff: sdk.DiffConfig{
+			Enabled:        cfg.Diff.Enabled,
+			FailOnBreaking: cfg.Diff.FailOnBreaking,
+		},
+	}
+}