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>

fsharp/tests/M11Pong.fs

@@ -134,6 +134,10 @@ let tests =
             Expect.equal (out |> List.map (fun s -> s.Held.Up)) [ false; false; true; true ] "held up"
             Expect.equal out[3].Player 20 "player moved up")
 
+        testCase "pongMain: after ten seconds in a background tab the match advances by 250 ms, not by ten seconds" (fun () ->
+            let _, afterFirst = Stream.step (Time 0L) (IO.trace 42u (pongMain ())).Result
+            Expect.equal (List.length (fst (Stream.step (Time 10000L) afterFirst))) 8 "eight drawings")
+
         testCase "pongMain asks for a seed, draws the new match first, and then the updated one" (fun () ->
             let traced = IO.trace 42u (pongMain ())
             Expect.equal traced.Ops [ IO.RandomSeed ] "ops"