feat(course): audit fixes and twelve extensions (Modules 7b, 12, 13)

Audit pass:
- Frame rule counts frames since the last move, so every step lasts
  exactly movesEvery(score) frames, also right after a speed-up
- clampTime + MAX_GAP_MS: a hidden tab no longer replays the whole gap
- Pong Restart keeps held keys
- Fact corrections (mulberry32 output coverage, Haskell IO, uniform)
- New fixture cases from a mutation analysis

Extensions (all three tracks, shared fixtures, course text):
- Turn queue (Exercise 10.6), persisted high score (10.7),
  replay viewer (10.8), play() end-to-end helper (9.5)
- Optional State (4.7) and optional Module 7b, stack-safe IO
- Module 12, property-based testing with generators, shrinking,
  invariants and a model-based oracle
- Module 13, Conway's Life with a Click event
- JS type checking via jsconfig, JSDoc and types.d.ts
- Maintainer tools: scripts/mutate.mjs, scripts/typecheck-js.sh,
  Playwright end-to-end suite (e2e/, scripts/e2e.sh)

Docs: docs/contract.md is the canonical contract; specs and build log
under docs/superpowers.

Verified: JS 728, Scala 689, F# 691 unit tests; stubs and progression
M01-M13 and M07b; 176 end-to-end tests on Chromium and WebKit.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

js/solutions/pong/model.js

@@ -3,6 +3,7 @@
 /** @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 */
+/** @typedef {{tag: 'Press', key: 'Up'|'Down'} | {tag: 'Release', key: 'Up'|'Down'} | {tag: 'Frame'} | {tag: 'Restart'}} PongAction */
 
 // The court, in cells. `player` and `cpu` are the y of the top cell of each paddle.
 export const W = 80
@@ -17,6 +18,7 @@ export const CPU_X = 77
 /** Points needed to win the match. */
 export const WIN = 5
 
+/** @type {(seed: number) => PongState} */
 export const initialPong = (seed) => ({
   ball: { x: 40, y: 25 },
   vel: { dx: 1, dy: 1 },
@@ -29,7 +31,8 @@ export const initialPong = (seed) => ({
   frame: 0,
 })
 
-/** Everything that can happen in a match, as data. */
+/** Everything that can happen in a match, as data.
+ * @type {{Press: (key: 'Up'|'Down') => PongAction, Release: (key: 'Up'|'Down') => PongAction, Frame: PongAction, Restart: PongAction}} */
 export const PongAction = {
   Press: (key) => ({ tag: 'Press', key }),
   Release: (key) => ({ tag: 'Release', key }),