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/M08Stream.fs

@@ -24,6 +24,9 @@ let tests =
         testCase "interval emits several multiples after one big time jump" (fun () ->
             Expect.equal (Stream.run [ Time 35L ] (Stream.interval 10L)) [ 10L; 20L; 30L ] "ticks")
 
+        testCase "interval 1 emits every millisecond crossed" (fun () ->
+            Expect.equal (Stream.run [ Time 1L; Time 3L ] (Stream.interval 1L)) [ 1L; 2L; 3L ] "ticks")
+
         testCase "interval ignores key events" (fun () ->
             Expect.equal (Stream.run [ KeyDown "a"; KeyUp "a" ] (Stream.interval 10L)) [] "ticks")