One invalid or null entry in commands.json makes KeybindingManager.InitializeAsync throw, although a syntactically corrupt commands.json is tolerated #133

What's wrong

This is the commands.json counterpart of #125, which covers only profiles.json. JsonKeybindingRepository.LoadCommandsAsync (Keybinding/Services/JsonKeybindingRepository.cs:~170-195) catches only JsonException. Inside the same try, .Select(dto => new Command(dto.Id, dto.Name, dto.Description, dto.Category)) throws ArgumentException for a blank id or name, and NullReferenceException for a null array element. KeybindingManager.InitializeAsync loads commands before profiles, so the whole startup fails.

Repro (verified against the built library)

With a valid profiles.json in place, write commands.json and call await new KeybindingManager(dir).InitializeAsync():

Why it matters

A single hand-edited or partially migrated entry prevents the application from starting. A file that is completely unparseable is handled gracefully, so the behaviour is also inconsistent.

Suggested fix

Convert each DTO in its own guarded step: skip null DTOs, and catch ArgumentException per entry so a bad entry is dropped rather than failing the load. The same pattern fits #125. Note that profiles.json also has null-shaped cases that throw NullReferenceException/ArgumentNullException ([null], "chords":{"a":null}, "notes":null), so catching ArgumentException alone would not be enough there either.

Acceptance: each of the three bad inputs above loads file.save and InitializeAsync does not throw. Add tests next to the existing corrupted-file test.