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/test/m09-app.test.js

@@ -1,11 +1,12 @@
 import test from 'node:test'
 import assert from 'node:assert/strict'
-import { states, classicActions, render, main, TICK_MS } from '../src/app.js'
+import { states, classicActions, render, main, play, TICK_MS } from '../src/app.js'
 import { run } from '../src/stream.js'
 import { trace } from '../src/io.js'
 import { view } from '../src/view.js'
 import { newGame } from '../src/spawn.js'
 import { Action } from '../src/model.js'
+import { history } from '../src/game.js'
 import { freeze } from './helpers.js'
 import { classicMain } from './m09-helpers.js'
 
@@ -33,12 +34,17 @@ test('m09 states starts with the new game, then yields one state per action', ()
 test('m09 render draws the whole view of the state', () =>
   assert.deepStrictEqual(trace(render(newGame(42)), 0).ops, view(newGame(42)).map((shape) => ({ tag: 'Draw', shape }))))
 
+// Module 10 (Exercise 10.7) makes `main` also load the stored best and draw one more shape after the game's view,
+// so this test accepts both versions; m10 pins the final one exactly.
 test('m09 main asks for a random seed, then builds the stream from it', () => {
   const { ops, result: stream } = trace(main, 42)
-  assert.deepStrictEqual(ops, [{ tag: 'RandomSeed' }])
+  assert.deepStrictEqual(ops[0], { tag: 'RandomSeed' })
+  assert.ok(ops.length === 1 || (ops.length === 2 && ops[1].tag === 'LoadBest'),
+    `main may only ask for the seed (and, from m10 on, the stored best); it asked for ${JSON.stringify(ops)}`)
   const [outs] = stream.step(time(0))
   assert.equal(outs.length, 1)
-  assert.deepStrictEqual(trace(outs[0], 0).ops, trace(render(newGame(42)), 0).ops)
+  const expected = trace(render(newGame(42)), 0).ops
+  assert.deepStrictEqual(trace(outs[0], 0).ops.slice(0, expected.length), expected)
 })
 
 // `main` itself switches to speedActions in m10, so the 150 ms behaviour is checked on the same program built from classicActions.
@@ -59,3 +65,19 @@ test('m09 main draws again once time has passed', () => {
   assert.equal(first.length, 1)
   assert.ok(later.length >= 1)
 })
+
+// ---- play: the whole program in one equality (Exercise 9.5)
+
+const drawOps = (state) => view(state).map((shape) => ({ tag: 'Draw', shape }))
+
+test('m09 play on the classic program equals the scenes of the expected states', () => {
+  const events = freeze([time(150), down('ArrowUp'), down('x'), time(300), time(310)])
+  const expectedStates = history(newGame(42), [Action.Tick, Action.Turn('Up'), Action.Tick])
+  assert.deepStrictEqual(play(classicMain, 42, events), expectedStates.map(drawOps))
+})
+
+test('m09 play with no events gives no drawings', () =>
+  assert.deepStrictEqual(play(classicMain, 42, []), []))
+
+test('m09 play uses the seed for the program\'s RandomSeed', () =>
+  assert.deepStrictEqual(play(classicMain, 7, freeze([time(0)])), [drawOps(newGame(7))]))