Initial boilerplate scaffold for continuum-schemas

Protobuf data model (Template/PrintJob/MaterialProfile/PrintParameters)
with codegen targets for TypeBox+TS types (packages/ts-types) and
prost-derived Rust structs (packages/rust-types).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packages/rust-types/src/lib.rs

@@ -0,0 +1,9 @@
+pub mod continuum {
+    pub mod v1 {
+        include!(concat!(env!("OUT_DIR"), "/continuum.v1.rs"));
+    }
+}
+
+pub use continuum::v1::{
+    MaterialProfile, PrintJob, PrintJobStatus, PrintParameters, Template,
+};