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/ball.lua

@@ -58,14 +58,14 @@ end
 function draw()
     renderer.clear(false)
     
-    -- Draw ball
-    renderer.circle(game.vars.ball_x, game.vars.ball_y, game.vars.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), game.vars.radius, true, true)
     
     -- Draw trail (previous positions)
     local trail_radius = game.vars.radius - 2
     if trail_radius > 2 then
-        renderer.circle(game.vars.ball_x - game.vars.vel_x, 
-                       game.vars.ball_y - game.vars.vel_y, 
+        renderer.circle(math.floor(game.vars.ball_x - game.vars.vel_x + 0.5), 
+                       math.floor(game.vars.ball_y - game.vars.vel_y + 0.5), 
                        trail_radius, true, false)
     end
     
@@ -80,5 +80,5 @@ function draw()
     -- Draw velocity vector
     local arrow_x = game.vars.ball_x + game.vars.vel_x * 3
     local arrow_y = game.vars.ball_y + game.vars.vel_y * 3
-    renderer.line(game.vars.ball_x, game.vars.ball_y, arrow_x, arrow_y, true, 2)
+    renderer.line(math.floor(game.vars.ball_x + 0.5), math.floor(game.vars.ball_y + 0.5), math.floor(arrow_x + 0.5), math.floor(arrow_y + 0.5), true, 2)
 end