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>

proto/continuum/v1/print_params.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package continuum.v1;
+
+message PrintParameters {
+  double layer_height_mm = 1;
+  int32 infill_percent = 2;
+  string infill_pattern = 3;
+  double print_speed_mm_s = 4;
+  bool supports_enabled = 5;
+  int32 wall_count = 6;
+}