Pull Request Description

Simplified and improved the MVC State Machine architecture by removing unnecessary abstractions, applying SOLID principles, and introducing a hybrid approach that combines the benefits of generic typing with interface flexibility.

What does this PR change?

1. Removed TContext from State Machine.
Context from the StateMachine is replaced by direct injection via constructor, because Context abstraction had several issues:

• States were using it only partially and some states were not using it at all — creates unneeded coupling
• It can easily become a "God Object"
• It was violating the "Law of Demeter"
• Dependencies of the state were obfuscated

Replaced solution improves encapsulation and readability — it is clear what is the dependency of each state.
Deleted files:
ChatStateContext.cs
ChatInputStateContext.cs

2. Removed State Machine injection into base state
Similarly, injection of stateMachine and its disposeCancellationToken into the state were replaced by direct injection in the state constructor, since not every state needed it. Indeed, only one state was depending on the disposeToken, and only states that perform transitions need the machine reference.

3. Removed unused Update/LateUpdate methods (YAGNI)
Unused methods such as Update(float deltaTime) and LateUpdate(float deltaTime) were removed, since no state was using them. Moreover, I don't see it coming for such UI-based state machine. More probably, we will extend state machine with transitions rather than with Update-loop behavior.

4. Replaced CRTP with Interface-based approach
CRTP (Curiously Recurring Template Pattern) for MVCState was replaced by a simplified approach via interfaces:

Before (CRTP):

public abstract class MVCState<TBaseState> where TBaseState : MVCState<TBaseState>
public class ChatState : MVCState<ChatState>

After (Interfaces):

// IExitableState ( Exit only)
//     ├── IState ( Enter without parameters)
//     └── IPayloadedState<T> (Enter with parameters)

public interface IExitableState { void Exit(); }
public interface IState : IExitableState { void Enter(); }
public interface IPayloadedState<in TPayload> : IExitableState { void Enter(TPayload payload); }

5. Hybrid Generic + Interface approach for State Machine
Combined the best of both worlds — typed CurrentState with interface flexibility:

public class MVCStateMachine<TBaseState> : IDisposable 
    where TBaseState : class, IExitableState
{
    public TBaseState? CurrentState { get; }  // Typed!
    
    public void Enter<TState>() where TState : TBaseState, IState;
    public void Enter<TState, TPayload>(TPayload payload) where TState : TBaseState, IPayloadedState<TPayload>;
}

Benefits:
✅ Compile-time type safety for CurrentState
✅ Support for payloaded states via IPayloadedState<T>
✅ Simpler to understand than CRTP
✅ Flexible — states can implement multiple interfaces

6. Simplified IndependentMVCState
Removed unnecessary generic layers and context from IndependentMVCState. Now it's a single simple class with Activate()/Deactivate() pattern.

Migration
States now receive their dependencies explicitly via constructor:

// Before: dependencies hidden in context
public class MyState : MVCState<MyState, MyContext> { }

// After: explicit dependencies
public class MyState : IState
{
    public MyState(MVCStateMachine<BaseState> machine, SomeDependency1 dep1, SomeDependency2 dep2) { }
}

Files Changed

• MVCStateMachine.cs — rewritten with generic + interface approach
• MVCState.cs — deleted, replaced by IState.cs
• IState.cs — new, contains IExitableState, IState, IPayloadedState<T>
• IndependentMVCState.cs — simplified
• All state implementations updated to use new interfaces
• All context files deleted

Test Instructions

This refactor touches mainly chat, but without adding or changing its functionality.
In theory, chat should work as in current dev, so please make a regression test on the chat features.
If possible, please verify that found issue is not presented in the dev

Quality Checklist

• Changes have been tested locally
• Documentation has been updated (if required)
• Performance impact has been considered
• For SDK features: Test scene is included

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