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/build.rs

@@ -0,0 +1,27 @@
+use std::path::PathBuf;
+
+fn main() {
+    let proto_root = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("../../proto")
+        .canonicalize()
+        .expect("proto root must exist");
+
+    let proto_files = [
+        proto_root.join("continuum/v1/material.proto"),
+        proto_root.join("continuum/v1/print_params.proto"),
+        proto_root.join("continuum/v1/template.proto"),
+        proto_root.join("continuum/v1/print_job.proto"),
+    ];
+
+    for file in &proto_files {
+        println!("cargo:rerun-if-changed={}", file.display());
+    }
+
+    let mut config = prost_build::Config::new();
+    config.type_attribute(".", "#[derive(serde::Serialize, serde::Deserialize)]");
+    config.type_attribute(".", "#[serde(rename_all = \"camelCase\")]");
+
+    config
+        .compile_protos(&proto_files, &[proto_root])
+        .expect("failed to compile continuum .proto sources");
+}