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/counter.lua

@@ -40,8 +40,8 @@ function draw()
         local pos_text = "Last: (" .. tostring(game.vars.last_x) .. ", " .. tostring(game.vars.last_y) .. ")"
         renderer.text(20, game.height() - 30, pos_text, true)
         
-        -- Draw marker at last touch
-        renderer.circle(game.vars.last_x, game.vars.last_y, 5, true, false)
+        -- Draw marker at last touch (convert to integers)
+        renderer.circle(math.floor(game.vars.last_x + 0.5), math.floor(game.vars.last_y + 0.5), 5, true, false)
     end
     
     -- Draw instructions