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>

fixtures/m13-life-step.json

@@ -0,0 +1,20 @@
+{
+  "function": "lifeStep",
+  "cases": [
+    {"name":"an-empty-board-stays-empty","args":[[]],"expected":[]},
+    {"name":"a-lonely-cell-dies","args":[[{"x":5,"y":5}]],"expected":[]},
+    {"name":"two-cells-die-of-loneliness","args":[[{"x":5,"y":5},{"x":6,"y":5}]],"expected":[]},
+    {"name":"a-block-is-stable","args":[[{"x":5,"y":5},{"x":6,"y":5},{"x":5,"y":6},{"x":6,"y":6}]],"expected":[{"x":5,"y":5},{"x":6,"y":5},{"x":5,"y":6},{"x":6,"y":6}]},
+    {"name":"a-horizontal-blinker-turns-vertical","args":[[{"x":4,"y":5},{"x":5,"y":5},{"x":6,"y":5}]],"expected":[{"x":5,"y":4},{"x":5,"y":5},{"x":5,"y":6}]},
+    {"name":"a-vertical-blinker-turns-horizontal","args":[[{"x":5,"y":4},{"x":5,"y":5},{"x":5,"y":6}]],"expected":[{"x":4,"y":5},{"x":5,"y":5},{"x":6,"y":5}]},
+    {"name":"three-cells-in-an-l-give-birth-to-a-block","args":[[{"x":5,"y":5},{"x":6,"y":5},{"x":5,"y":6}]],"expected":[{"x":5,"y":5},{"x":6,"y":5},{"x":5,"y":6},{"x":6,"y":6}]},
+    {"name":"a-cell-with-four-neighbours-dies-of-overcrowding","args":[[{"x":5,"y":4},{"x":4,"y":5},{"x":5,"y":5},{"x":6,"y":5},{"x":5,"y":6}]],"expected":[{"x":4,"y":4},{"x":5,"y":4},{"x":6,"y":4},{"x":4,"y":5},{"x":6,"y":5},{"x":4,"y":6},{"x":5,"y":6},{"x":6,"y":6}]},
+    {"name":"a-glider-moves-and-the-result-is-sorted-row-major","args":[[{"x":1,"y":0},{"x":2,"y":1},{"x":0,"y":2},{"x":1,"y":2},{"x":2,"y":2}]],"expected":[{"x":0,"y":1},{"x":2,"y":1},{"x":1,"y":2},{"x":2,"y":2},{"x":1,"y":3}]},
+    {"name":"a-block-in-the-corner-is-stable","args":[[{"x":0,"y":0},{"x":1,"y":0},{"x":0,"y":1},{"x":1,"y":1}]],"expected":[{"x":0,"y":0},{"x":1,"y":0},{"x":0,"y":1},{"x":1,"y":1}]},
+    {"name":"a-block-in-the-far-corner-is-stable","args":[[{"x":38,"y":28},{"x":39,"y":28},{"x":38,"y":29},{"x":39,"y":29}]],"expected":[{"x":38,"y":28},{"x":39,"y":28},{"x":38,"y":29},{"x":39,"y":29}]},
+    {"name":"a-blinker-on-the-top-edge-cannot-grow-beyond-it","args":[[{"x":4,"y":0},{"x":5,"y":0},{"x":6,"y":0}]],"expected":[{"x":5,"y":0},{"x":5,"y":1}]},
+    {"name":"a-blinker-on-the-right-edge-does-not-wrap-to-the-left-edge","args":[[{"x":39,"y":9},{"x":39,"y":10},{"x":39,"y":11}]],"expected":[{"x":38,"y":10},{"x":39,"y":10}]},
+    {"name":"cells-on-opposite-edges-are-not-neighbours","args":[[{"x":39,"y":9},{"x":0,"y":10},{"x":39,"y":10},{"x":39,"y":11}]],"expected":[{"x":38,"y":10},{"x":39,"y":10}]},
+    {"name":"a-blinker-on-the-bottom-edge-cannot-grow-beyond-it","args":[[{"x":10,"y":29},{"x":11,"y":29},{"x":12,"y":29}]],"expected":[{"x":11,"y":28},{"x":11,"y":29}]}
+  ]
+}