feat(js): m05 game and m06 view with fixtures and tests

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

js/src/game.js

@@ -0,0 +1,14 @@
+import { todo } from './todo.js'
+
+/**
+ * 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.
+ */
+export const update = (state, action) => todo('m05')
+
+/** Apply all actions in order, starting from `state`, and return the final state. */
+export const replay = (state, actions) => todo('m05')
+
+/** Like `replay`, but keep every state: `[state, afterFirst, afterSecond, ...]`, so its length is `actions.length + 1`. */
+export const history = (state, actions) => todo('m05')