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/util.js

@@ -1,18 +1,23 @@
 // m01 util: small helpers used by every later module.
 
-/** `range(n)` is `[0, 1, ..., n-1]`; `range(0)` is `[]`. */
+/** `range(n)` is `[0, 1, ..., n-1]`; `range(0)` is `[]`.
+ * @type {(n: number) => number[]} */
 export const range = (n) => Array.from({ length: n }, (_, i) => i)
 
-/** `xs` without its last element; an empty list stays empty. Never mutates `xs`. */
+/** `xs` without its last element; an empty list stays empty. Never mutates `xs`.
+ * @type {<A>(xs: A[]) => A[]} */
 export const dropLast = (xs) => xs.slice(0, -1)
 
-/** True if some element `x` of `xs` satisfies `eq(x, p)`. `eq` lets callers compare structurally (e.g. `pointEquals`). */
+/** True if some element `x` of `xs` satisfies `eq(x, p)`. `eq` lets callers compare structurally (e.g. `pointEquals`).
+ * @type {<A, B>(xs: A[], p: B, eq: (x: A, p: B) => boolean) => boolean} */
 export const contains = (xs, p, eq) => xs.some((x) => eq(x, p))
 
-/** `pipe(x, f, g)` is `g(f(x))`: thread a value through functions left to right. */
+/** `pipe(x, f, g)` is `g(f(x))`: thread a value through functions left to right.
+ * @type {(x: any, ...fns: ((a: any) => any)[]) => any} */
 export const pipe = (x, ...fns) => fns.reduce((acc, f) => f(acc), x)
 
-/** `compose(f, g)(x)` is `f(g(x))`: functions applied right to left. */
+/** `compose(f, g)(x)` is `f(g(x))`: functions applied right to left.
+ * @type {(...fns: ((a: any) => any)[]) => (x: any) => any} */
 export const compose = (...fns) => (x) => fns.reduceRight((acc, f) => f(acc), x)
 
 /**
@@ -21,6 +26,7 @@ export const compose = (...fns) => (x) => fns.reduceRight((acc, f) => f(acc), x)
  * We recurse even into children that are already frozen (a frozen parent can still hold
  * unfrozen children). `ancestors` is the path from the root to `obj`; passing it down
  * (instead of keeping a shared "seen" set) stops cyclic structures without any mutable state.
+ * @type {<T>(obj: T, ancestors?: unknown[]) => T}
  */
 export const deepFreeze = (obj, ancestors = []) => {
   if (obj === null || typeof obj !== 'object' || ancestors.includes(obj)) return obj