feat: resolve file-local import namespaces

source/diagnostics/diagnostics.hon

@@ -66,6 +66,9 @@ Code :: enum {
     import_cycle
     invalid_import_path
     package_unavailable
+    namespace_not_value
+    not_namespace
+    invalid_import_alias
 }
 
 Diagnostic :: struct {
@@ -153,5 +156,8 @@ messages :: $enummap.init(Code, []u8, {
     import_cycle = "package import cycle",
     invalid_import_path = "invalid import path",
     package_unavailable = "cannot load package directory",
+    namespace_not_value = "package namespace cannot be used as a value",
+    not_namespace = "member selection requires a package namespace",
+    invalid_import_alias = "import requires an explicit valid identifier alias",
 })