Fix chat send button not re-enabling

[Alexia-Claudia-Micu]

Pull Request

🤨 Rationale

The send button is disabled when either sendDisabled is true (consumer side) or the text box is empty. The bug was that shouldDisableSendButton combined both conditions and its result was held in isInputEmpty (which only refreshed on text events).

Since sendDisabled is an attribute, its state change never caused IsInputEmpty to refresh.

👩‍💻 Implementation

IsInputEmpty now only tracks this.textArea!.value.length === 0 leaving the button state to be calculated in the template: ?disabled=${x => (x.processing ? false : (x.sendDisabled || x.isInputEmpty))}

🧪 Testing

Added unit test.

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[Alexia-Claudia-Micu]

@rajsite Could you review this PR when you have the time as well? It is a fix for: #2981