Note is marked [JsonConstructor] but System.Text.Json serializes its key as a char array and can't deserialize it #122

What's wrong

Note (Keybinding/Models/MusicalTypes.cs, around line 17) has a [JsonConstructor], which tells consumers they can serialize it directly. However, NoteName is a SemanticString, and System.Text.Json treats it as a collection of chars:

JsonSerializer.Serialize(new Note("Ctrl"));            // {"Key":["C","T","R","L"]}
JsonSerializer.Deserialize<Note>("{\"Key\":\"CTRL\"}"); // JsonException: could not be converted to NoteName. Path: $.Key

Deserializing the library's own serialized output also fails: NotSupportedException: The collection type 'NoteName' is abstract, an interface, or is read only.

The library's own persistence goes through string DTOs, so it isn't affected. Any consumer who stores Note, Chord or Phrase in their own settings JSON gets unreadable output that can't be loaded back.

Reproduced

[TestMethod] public void NoteJsonSerialize() => Assert.AreEqual("{\"Key\":\"CTRL\"}", JsonSerializer.Serialize(new Note("Ctrl")));
[TestMethod] public void NoteJsonDeserialize() => Assert.AreEqual(new Note("Ctrl"), JsonSerializer.Deserialize<Note>("{\"Key\":\"ctrl\"}"));

Both tests fail as described above.

Suggested fix

Add a JsonConverter<Note> (via [JsonConverter]) that writes the key as a string and reads it back through the normalizing Note(string) constructor. Alternatively, register a SemanticString converter for NoteName. If direct serialization isn't meant to be supported, remove [JsonConstructor] so the type stops advertising it.

Acceptance: Note round-trips through JsonSerializer as {"Key":"CTRL"}, and lowercase or alias input deserializes to the canonical note.