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/m01-util.test.js

@@ -49,6 +49,13 @@ test('m01 deepFreeze reaches unfrozen children of an already-frozen parent', ()
   const o = deepFreeze({ a: Object.freeze({ b: { c: 1 } }) })
   assert.ok(Object.isFrozen(o.a.b))
 })
+test('m01 deepFreeze leaves null and other non-objects alone', () => {
+  const o = deepFreeze({ apple: null, score: 3, name: 'x', missing: undefined })
+  assert.ok(Object.isFrozen(o))
+  assert.equal(deepFreeze(null), null)
+  assert.equal(deepFreeze(7), 7)
+})
+
 test('m01 deepFreeze handles cyclic objects', () => {
   const o = { child: {} }
   o.child.parent = o