DMX4001: Dart 3.13 primary constructors reported as invalid Dart

Start with the dmx build and dmx watch entry points and reproduce the failure against a .dart file containing a Dart 3.13 primary constructor. Trace how every .dart file under lib/ is parsed, then verify that primary constructors parse successfully and that an unrelated unannotated file no longer blocks annotated generation or watch runs.

Summary

dmx 0.3.0 reports DMX4001: input is not valid Dart on files that compile with Dart 3.13. The parser does not accept primary constructors (class const Foo(...) / class Foo(...)).
Because dmx build / dmx watch parse every .dart file under the given path (not only @dmx(...) classes), a single primary constructor anywhere in lib/ makes a project-wide generate/watch run fail.

Environment

• dmx: 0.3.0 (VS Code extension bundled CLI, also used from terminal)
• Dart: 3.13.0
• Flutter: 3.47.0
• OS: macOS (Apple Silicon)

Reproduction

1. Create a file that is valid Dart 3.13, with no @dmx annotation:

class const ZipAddressModel({
  required final String pref,
  required final String city,
  required final String town,
});

2. Run:

dmx build lib --insert-regions
# or
dmx watch lib

Actual

error: DMX4001: input is not valid Dart at line 2, column 13

The column points at const in class const ZipAddressModel({.
The same error appears on every primary-constructor class in the tree, for example:

error: lib/core/api/api.dart: DMX4001: input is not valid Dart at line 524, column 13
error: lib/features/wallet/schemas/zip_address_model.dart: DMX4001: input is not valid Dart at line 2, column 13

dmx watch lib still prints dmx: watching 1 path(s), but those files never get a usable parse.
dart analyze on the same files reports no issues.

Expected

• Dart 3.13 primary constructors should parse as valid input.
• Files without @dmx(...) should not block generate/watch for annotated classes in the same tree.
• Alternatively, build / watch should skip files they cannot (yet) parse, instead of failing the whole run.

Workaround

Point dmx at a single experimental file instead of the whole lib/ directory:

dmx build path/to/annotated_file.dart --insert-regions
dmx watch path/to/annotated_file.dart

That is not viable for a real app whose lib/ already uses primary constructors.

Notes

Related, but separate: DMX2001 requires an explicit type on fields such as final _fieldKey = GlobalKey<...>(). That is valid inferred Dart; calling out in case the parser is intentionally stricter than the language.
Happy to provide a minimal repo if useful.