feat(build): add optional content-hash based build cache to skip rebuilding unchanged Dockerfiles

ts/interfaces/index.ts

@@ -77,4 +77,17 @@ export interface IBuildCommandOptions {
   platform?: string;    // Single platform override (e.g., 'linux/arm64')
   timeout?: number;     // Build timeout in seconds
   noCache?: boolean;    // Force rebuild without Docker layer cache (--no-cache)
+  cached?: boolean;     // Skip builds when Dockerfile content hasn't changed
+}
+
+export interface ICacheEntry {
+  contentHash: string;   // SHA-256 hex of Dockerfile content
+  imageId: string;       // Docker image ID (sha256:...)
+  buildTag: string;
+  timestamp: number;     // Unix ms
+}
+
+export interface ICacheData {
+  version: 1;
+  entries: { [cleanTag: string]: ICacheEntry };
 }