Add design containers with deduplicated blobs and JSON compatibility (#327)

* Add fast design containers with lossless deduplicated payloads

* Keep display caching opt-in to avoid default save overhead

crates/io/Cargo.toml

@@ -15,3 +15,6 @@ solidcraft-doc = { workspace = true }
 thiserror = { workspace = true }
 zip = { workspace = true }
 quick-xml = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+sha2 = { workspace = true }