feat(js): m11 pong capstone (model, rules, view, app, page) and polling smoke test

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

js/solutions/pong/model.js

@@ -0,0 +1,38 @@
+// m11 pong model: the same ideas as the snake model, for a different game.
+
+/** @typedef {{ball: {x: number, y: number}, vel: {dx: number, dy: number}, player: number, cpu: number,
+ *   held: {up: boolean, down: boolean}, score: {player: number, cpu: number},
+ *   status: 'Playing'|'Over', seed: number, frame: number}} PongState */
+
+// The court, in cells. `player` and `cpu` are the y of the top cell of each paddle.
+export const W = 80
+export const H = 50
+/** Pixels per cell. */
+export const PCELL = 8
+/** Paddle height in cells. */
+export const PADDLE = 8
+/** Column of the player's paddle (left) and the cpu's paddle (right). */
+export const PLAYER_X = 2
+export const CPU_X = 77
+/** Points needed to win the match. */
+export const WIN = 5
+
+export const initialPong = (seed) => ({
+  ball: { x: 40, y: 25 },
+  vel: { dx: 1, dy: 1 },
+  player: 21,
+  cpu: 21,
+  held: { up: false, down: false },
+  score: { player: 0, cpu: 0 },
+  status: 'Playing',
+  seed,
+  frame: 0,
+})
+
+/** Everything that can happen in a match, as data. */
+export const PongAction = {
+  Press: (key) => ({ tag: 'Press', key }),
+  Release: (key) => ({ tag: 'Release', key }),
+  Frame: { tag: 'Frame' },
+  Restart: { tag: 'Restart' },
+}