feat(devops): add ImageSource interface

Defines common interface for GitHub, Registry, and CDN sources.

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

pkg/devops/sources/source.go

@@ -0,0 +1,31 @@
+// Package sources provides image download sources for core-devops.
+package sources
+
+import (
+	"context"
+)
+
+// ImageSource defines the interface for downloading dev images.
+type ImageSource interface {
+	// Name returns the source identifier.
+	Name() string
+	// Available checks if this source can be used.
+	Available() bool
+	// LatestVersion returns the latest available version.
+	LatestVersion(ctx context.Context) (string, error)
+	// Download downloads the image to the destination path.
+	// Reports progress via the callback if provided.
+	Download(ctx context.Context, dest string, progress func(downloaded, total int64)) error
+}
+
+// SourceConfig holds configuration for a source.
+type SourceConfig struct {
+	// GitHub configuration
+	GitHubRepo string
+	// Registry configuration
+	RegistryImage string
+	// CDN configuration
+	CDNURL string
+	// Image name (e.g., core-devops-darwin-arm64.qcow2)
+	ImageName string
+}