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>

course/05-folding-time.md

@@ -137,7 +137,7 @@ List.scan apply 100 txs                // [100; 150; 130; 135]
 
 Because a game is `fold(update, start, actions)` and `update` is pure:
 
-- **Replays.** To store a whole game you do not need a video. You need the start state, which is fully determined by the seed (`newGame(seed)`), and the list of actions. Replaying them through `update` reproduces every state exactly, apples included, because the random seed is in the state (Module 4).
+- **Replays.** To store a whole game you do not need a video. You need the start state, which is fully determined by the seed (`newGame(seed)`), and the list of actions. Replaying them through `update` reproduces every state exactly, apples included, because the random seed is in the state (Module 4). In Module 10 (section 9, Exercise 10.8) you build a replay viewer on exactly this: `history` of a recorded game, shown frame by frame, forwards and backwards.
 - **Deterministic tests.** A test is "this start, these actions, this expected end". No timers, no mocks, no sleeping. The fixture `twelve-actions-eat-one-apple` is a whole little game in one test case:
 
   ```
@@ -361,5 +361,6 @@ let history (state: GameState) (actions: Action list) : GameState list = List.sc
 - [Array.prototype.reduce (MDN)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce) — JavaScript's fold, including the empty-array pitfall.
 - [F# List module](https://fsharp.github.io/fsharp-core-docs/reference/fsharp-collections-listmodule.html) and [Scala List API](https://www.scala-lang.org/api/current/scala/collection/immutable/List.html) — `fold`/`scan` and `foldLeft`/`scanLeft`.
 - [The Elm Architecture](https://guide.elm-lang.org/architecture/) — model, update, view: the structure this course is building, from Elm's own guide.
+- [Martin Kleppmann, "Turning the database inside-out"](https://martin.kleppmann.com/2015/03/04/turning-the-database-inside-out.html) — a talk (with transcript) on treating the log of events as the source of truth and every table as a fold over it.
 - [Mealy machine (Wikipedia)](https://en.wikipedia.org/wiki/Mealy_machine) — a state machine whose step produces outputs from the current state and input; a preview of how Module 8 will model streams.
 - [Conal Elliott and Paul Hudak, "Functional Reactive Animation"](http://conal.net/papers/icfp97/) — the paper that started treating time-varying values and events as first-class values, the idea behind Modules 8 and 9.