feat: add compile-time type metadata reflection

source/diagnostics/diagnostics.hon

@@ -119,6 +119,8 @@ Code :: enum {
     invalid_generated_field_name
     invalid_struct_layout
     invalid_c_record_field_type
+    missing_metadata_import
+    invalid_metadata_abi
 }
 
 Diagnostic :: struct {
@@ -259,5 +261,7 @@ messages :: $enummap.init(Code, []u8, {
     invalid_generated_field_name = "generated field name must be an ASCII identifier",
     invalid_struct_layout = "generated record layout must be .auto or .c; C-layout records require at least one field",
     invalid_c_record_field_type = "record field is not a supported C-layout value type",
+    missing_metadata_import = "typeinfo! requires importing @std/meta",
+    invalid_metadata_abi = "@std/meta declarations do not match the compiler reflection ABI",
 })