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/m10-viewer-key.json

@@ -0,0 +1,19 @@
+{
+  "function": "viewerKey",
+  "cases": [
+    {"name":"ArrowRight-is-next","args":["ArrowRight"],"expected":{"tag":"Next"}},
+    {"name":"d-is-next","args":["d"],"expected":{"tag":"Next"}},
+    {"name":"D-is-next","args":["D"],"expected":{"tag":"Next"}},
+    {"name":"ArrowLeft-is-prev","args":["ArrowLeft"],"expected":{"tag":"Prev"}},
+    {"name":"a-is-prev","args":["a"],"expected":{"tag":"Prev"}},
+    {"name":"A-is-prev","args":["A"],"expected":{"tag":"Prev"}},
+    {"name":"Home-is-first","args":["Home"],"expected":{"tag":"First"}},
+    {"name":"End-is-last","args":["End"],"expected":{"tag":"Last"}},
+    {"name":"space-toggles-play","args":[" "],"expected":{"tag":"TogglePlay"}},
+    {"name":"ArrowUp-is-not-bound","args":["ArrowUp"],"expected":null},
+    {"name":"r-is-not-bound","args":["r"],"expected":null},
+    {"name":"constructor-is-not-bound","args":["constructor"],"expected":null},
+    {"name":"toString-is-not-bound","args":["toString"],"expected":null},
+    {"name":"empty-string-is-not-bound","args":[""],"expected":null}
+  ]
+}