games: 30 fps render loop + immediate Snake turns

Switched both games to a 30 fps render cap (FRAME_MS = 33 ms) for smoother,
more predictable frame pacing. Snake base speed raised to 150 px/sec (~60 ms
per step at cell=9) so turn commands take effect at the next step without
perceived lag. The buffered-direction model (latest keypress wins) is
unchanged — turns apply at the next step, which is immediate in snake terms.

Progressive difficulty (+1 px/sec per 5 food in Snake, +1 px/sec per 10 lines
in Tetris), edge wrap, Gameboy-style beveled blocks, and all controls are
unchanged.

src/games/snake.cpp

@@ -107,7 +107,7 @@ static int foodx, foody;
 static int score = 0;
 static int best = 0;
 static int speed = 90;             // ms per step (derived from pps below)
-static int pps = 100;              // base speed px/sec; +1 px/sec per 5 food eaten
+static int pps = 150;              // base speed px/sec; +1 px/sec per 5 food eaten
 static unsigned long nextTick = 0;
 static bool running = true;
 static unsigned long now_ms() {
@@ -165,7 +165,7 @@ static void reset_game() {
   dirx = 1; diry = 0;
   ndirx = 1; ndiry = 0;
   score = 0;
-  pps = 100;
+  pps = 150;
   update_speed();
   place_food();
   state = PLAYING;
@@ -202,7 +202,7 @@ static void step() {
     score += 10;
     if (score > best) best = score;
     int food = score / 10;        // food items eaten so far
-    pps = 100 + food / 5;          // +1 px/sec per 5 food eaten (progressive difficulty)
+    pps = 150 + food / 5;          // +1 px/sec per 5 food eaten (progressive difficulty)
     update_speed();
     place_food();
   }
@@ -375,7 +375,7 @@ int main() {
   render();
 
   int xfd = ConnectionNumber(dpy);
-  const unsigned long FRAME_MS = 1000 / 60;  // 60 fps rendering
+  const unsigned long FRAME_MS = 1000 / 30;  // 30 fps rendering
   unsigned long lastFrame = now_ms();
 
   while (running) {

src/games/tetris.cpp

@@ -499,7 +499,7 @@ int main() {
   render();
 
   int xfd = ConnectionNumber(dpy);
-  const unsigned long FRAME_MS = 1000 / 60;  // 60 fps rendering
+  const unsigned long FRAME_MS = 1000 / 30;  // 30 fps rendering
   unsigned long lastFrame = now_ms();
 
   while (running) {