feat(js): m10 extensions (pause, restart, speed-up via Frame) with tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

js/src/game.js

@@ -1,9 +1,21 @@
 import { todo } from './todo.js'
 
+/**
+ * How many frames pass between game steps (m10): `max(2, 8 - floor(score / 3))`.
+ * Score 0-2 -> 8, 3-5 -> 7, ..., 18 and up -> 2.
+ */
+export const movesEvery = (score) => todo('m10')
+
 /**
  * The one function that says how the game changes: `(state, action) -> state`.
- * `Tick` runs a game step (`tick`), `Turn` asks to change direction (`turn`);
- * every other action returns the state unchanged for now.
+ *
+ * m05: `Tick` runs a game step (`tick`), `Turn` asks to change direction (`turn`);
+ * every other action returns the state unchanged.
+ *
+ * (m10) `TogglePause` switches Playing <-> Paused and does nothing in any other status.
+ * (m10) `Restart` gives `newGame(state.seed)`, whatever the status.
+ * (m10) `Frame` does nothing unless Playing; otherwise it adds 1 to `frame`, and when the new `frame` is a multiple of
+ * `movesEvery(score)` it also runs a game step (`tick`) on that incremented state.
  */
 export const update = (state, action) => todo('m05')