feat: WASD free-fly camera with F toggle

- Add ICameraController interface and FreeFlyCameraController.
- WASD moves, Q/E up/down, Shift sprint, right-mouse + mouse look.
- Toggle between Orbit and FreeFly with F key.
- OrbitCameraController now implements ICameraController.
- Update Program.cs to switch active controller on F.
- Update CORTEX_ENGINE_ARCHITECTURE.md with camera controls.
- Debug/Release/ReleaseAOT all build.

CORTEX_ENGINE_ARCHITECTURE.md

@@ -529,7 +529,9 @@ In Release (NativeAOT), the MCP server and ASP.NET Core are excluded. The AI can
 │   │   ├── Sdl3Window.cs                 # SDL3 window wrapper
 │   │   ├── Timing.cs                     # DeltaTime, fixed timestep
 │   │   ├── InputMapping.cs               # Keyboard, mouse, gamepad input
+│   │   ├── ICameraController.cs            # Camera controller interface
 │   │   ├── OrbitCameraController.cs      # Mouse orbit camera
+│   │   ├── FreeFlyCameraController.cs    # WASD + mouse look camera
 │   │   └── Components/                   # Transform, Camera, Light, Material, Mesh
 │   │
 │   ├── Engine.Data/
@@ -760,7 +762,9 @@ dotnet run --project src/CortexEngine.App/CortexEngine.App.csproj
 
 - `SDL3 2026.520.0` API: `SDL_Init` returns `SDLBool`, `SDL_PollEvent` returns `SDLBool`, `evt.type` is `uint`.
 - Keyboard: `evt.key.key`; Mouse: `evt.motion.x`, `evt.motion.y`, `evt.wheel.y`.
-- Orbit camera: right mouse drag rotates, mouse wheel zooms, `ESC` exits.
+- **Orbit camera** (по умолчанию): правый клик + движение мыши — вращать, колесо — zoom.
+- **FreeFly camera** (переключается клавишей `F`): `WASD` — двигаться, `Q`/`E` — вниз/вверх, `Shift` — ускорение, правый клик + мышь — осмотр.
+- `ESC` — выход.
 
 ### 13.5 MCP Client Config
 

src/CortexEngine.App/Program.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Numerics;
 using Engine.AI;
+using SDL;
 using SixLabors.ImageSharp;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
@@ -73,7 +74,12 @@ class Program
                 .Set(new Transform(new Vector3(0.0f, 0.0f, 0.0f), Quaternion.Identity, Vector3.One))
                 .Set(new Light(new Vector3(0.0f, 1.0f, 0.0f), new Vector3(0.15f, 0.15f, 0.2f), 0.3f));
 
-            var orbit = new OrbitCameraController(cameraEntity, new Vector3(0.0f, 0.5f, 0.0f));
+            ICameraController[] cameraControllers =
+            [
+                new OrbitCameraController(cameraEntity, new Vector3(0.0f, 0.5f, 0.0f)),
+                new FreeFlyCameraController(cameraEntity)
+            ];
+            var activeControllerIndex = 0;
 
             var texturePath = GenerateCheckerboardTexture("Content/checkerboard.png", 256);
 
@@ -159,8 +165,15 @@ class Program
                     camera.AspectRatio = (float)lastWidth / lastHeight;
                 }
 
-                // Update orbit camera from mouse input.
-                orbit.Update(input, (float)timing.DeltaTime);
+                // Toggle camera controller with F.
+                if (input.IsKeyPressed(SDL_Keycode.SDLK_F))
+                {
+                    activeControllerIndex = (activeControllerIndex + 1) % cameraControllers.Length;
+                    Console.WriteLine($"Camera controller: {cameraControllers[activeControllerIndex].Name}");
+                }
+
+                // Update active camera controller from input.
+                cameraControllers[activeControllerIndex].Update(input, (float)timing.DeltaTime);
 
                 // Slowly rotate the model so we can see it in 3D.
                 ref var modelTransform = ref model.Ensure<Transform>();

src/Engine.Core/FreeFlyCameraController.cs

@@ -0,0 +1,114 @@
+using System;
+using System.Numerics;
+using Flecs.NET.Core;
+using SDL;
+using Engine.Core.Components;
+
+namespace Engine.Core;
+
+/// <summary>
+/// First-person / free-fly camera controller.
+/// WASD moves on the ground plane, Q/E move up/down, Shift boosts speed.
+/// Mouse look while right mouse button is held.
+/// </summary>
+public sealed class FreeFlyCameraController : ICameraController
+{
+    private readonly Entity _cameraEntity;
+    private float _yaw;
+    private float _pitch;
+    private float _speed = 3.0f;
+    private float _fastSpeed = 8.0f;
+    private float _mouseSensitivity = 0.003f;
+    private int _lastMouseX;
+    private int _lastMouseY;
+    private bool _wasRightMouseDown;
+    private Vector3 _position;
+
+    public string Name => "FreeFly";
+
+    public FreeFlyCameraController(Entity cameraEntity)
+    {
+        _cameraEntity = cameraEntity;
+        var camera = cameraEntity.Get<Camera>();
+        _position = camera.Position;
+
+        var forward = Vector3.Normalize(camera.Target - camera.Position);
+        _pitch = MathF.Asin(-forward.Y);
+        _yaw = MathF.Atan2(forward.X, forward.Z);
+    }
+
+    public void Update(InputMapping input, float deltaTime)
+    {
+        var move = Vector3.Zero;
+        var forward = new Vector3(MathF.Sin(_yaw), 0.0f, MathF.Cos(_yaw));
+        var right = new Vector3(MathF.Cos(_yaw), 0.0f, -MathF.Sin(_yaw));
+        var up = Vector3.UnitY;
+
+        if (input.IsKeyDown(SDL_Keycode.SDLK_W))
+            move += forward;
+        if (input.IsKeyDown(SDL_Keycode.SDLK_S))
+            move -= forward;
+        if (input.IsKeyDown(SDL_Keycode.SDLK_A))
+            move -= right;
+        if (input.IsKeyDown(SDL_Keycode.SDLK_D))
+            move += right;
+        if (input.IsKeyDown(SDL_Keycode.SDLK_E))
+            move += up;
+        if (input.IsKeyDown(SDL_Keycode.SDLK_Q))
+            move -= up;
+
+        if (move.LengthSquared() > 0.0f)
+        {
+            move = Vector3.Normalize(move);
+            var speed = input.IsKeyDown(SDL_Keycode.SDLK_LSHIFT) ? _fastSpeed : _speed;
+            _position += move * speed * deltaTime;
+        }
+
+        if (input.MouseWheelDelta != 0)
+        {
+            _speed *= 1.0f + input.MouseWheelDelta * 0.1f;
+            _speed = Math.Clamp(_speed, 0.5f, 30.0f);
+        }
+
+        if (input.MouseRight)
+        {
+            if (!_wasRightMouseDown)
+            {
+                _lastMouseX = input.MouseX;
+                _lastMouseY = input.MouseY;
+                _wasRightMouseDown = true;
+            }
+            else
+            {
+                var dx = input.MouseX - _lastMouseX;
+                var dy = input.MouseY - _lastMouseY;
+                _yaw += dx * _mouseSensitivity;
+                _pitch += dy * _mouseSensitivity;
+                _pitch = Math.Clamp(_pitch, -MathF.PI / 2.0f + 0.01f, MathF.PI / 2.0f - 0.01f);
+                _lastMouseX = input.MouseX;
+                _lastMouseY = input.MouseY;
+            }
+        }
+        else
+        {
+            _wasRightMouseDown = false;
+        }
+
+        UpdateCamera();
+    }
+
+    private void UpdateCamera()
+    {
+        var camera = _cameraEntity.Get<Camera>();
+        camera.Position = _position;
+
+        var direction = new Vector3(
+            MathF.Cos(_pitch) * MathF.Sin(_yaw),
+            -MathF.Sin(_pitch),
+            MathF.Cos(_pitch) * MathF.Cos(_yaw));
+
+        camera.Target = _position + direction;
+        camera.Up = Vector3.UnitY;
+        _cameraEntity.Set(camera);
+    }
+}

src/Engine.Core/ICameraController.cs

@@ -0,0 +1,10 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Common interface for camera controllers (orbit, free-fly, etc.).
+/// </summary>
+public interface ICameraController
+{
+    string Name { get; }
+    void Update(InputMapping input, float deltaTime);
+}

src/Engine.Core/OrbitCameraController.cs

@@ -8,7 +8,7 @@ namespace Engine.Core;
 /// Orbit camera controller. Right mouse drag rotates around the target,
 /// mouse wheel zooms in/out.
 /// </summary>
-public sealed class OrbitCameraController
+public sealed class OrbitCameraController : ICameraController
 {
     private readonly Entity _cameraEntity;
     private float _distance;
@@ -19,6 +19,8 @@ public sealed class OrbitCameraController
     private int _lastMouseY;
     private bool _isDragging;
 
+    public string Name => "Orbit";
+
     public OrbitCameraController(Entity cameraEntity, Vector3? target = null)
     {
         _cameraEntity = cameraEntity;