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

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

js/solutions/game.js

@@ -0,0 +1,21 @@
+// m05 game: one `update` function turns every action into a new state; replay is a fold over actions.
+import { turn } from './rules.js'
+import { tick } from './spawn.js'
+
+/** Tick and Turn are handled here; other actions leave the state alone (m10 adds more). */
+export const update = (state, action) => {
+  switch (action.tag) {
+    case 'Tick': return tick(state)
+    case 'Turn': return turn(state, action.dir)
+    default: return state
+  }
+}
+
+/** Fold the actions over the state, left to right. */
+export const replay = (state, actions) => actions.reduce(update, state)
+
+/** Like replay, but keeps each intermediate state. Recursion instead of mutation: no array is ever pushed to. */
+export const history = (state, actions) =>
+  actions.length === 0
+    ? [state]
+    : [state, ...history(update(state, actions[0]), actions.slice(1))]