Fix Lua game float-to-int conversion errors for renderer.circle()

All games had the same issue: renderer.circle() requires integer arguments,
but float calculations produced non-integer coordinates.

Fixed in all games using math.floor(x + 0.5) for proper rounding:
- pong.lua: Ball position
- air_hockey.lua: Puck position
- asteroids.lua: Asteroid positions
- ball.lua: Ball and trail positions, velocity line
- breakout.lua: Ball position
- flappy_bird.lua: Bird Y position
- counter.lua: Last touch marker position
- snake.lua: Food position (center calculation)
- tic_tac_toe.lua: O circle center position

Also fixed floating-point coordinate calculations in ball and line
drawing to ensure all coordinates are integers.

games/lua_examples/pong.lua

@@ -109,8 +109,8 @@ function draw()
         renderer.rect(10, game.vars.paddle_left_y, PADDLE_WIDTH, PADDLE_HEIGHT, true, true)
         renderer.rect(game.width() - 10 - PADDLE_WIDTH, game.vars.paddle_right_y, PADDLE_WIDTH, PADDLE_HEIGHT, true, true)
         
-        -- Draw ball
-        renderer.circle(game.vars.ball_x, game.vars.ball_y, BALL_RADIUS, true, true)
+        -- Draw ball (convert to integers)
+        renderer.circle(math.floor(game.vars.ball_x + 0.5), math.floor(game.vars.ball_y + 0.5), BALL_RADIUS, true, true)
         
         -- Draw scores
         local left_score_text = tostring(game.vars.paddle_left_score)