docs: handoff, session log and pointers to the contract

docs/HANDOFF.md is the starting point for the next maintainer;
docs/superpowers/notes/2026-11-11-session-log.md records the day.
AGENTS.md, CLAUDE.md and README now point maintainers to the handoff
and to docs/contract.md.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

docs/superpowers/notes/2026-10-29-build-log.md

@@ -79,7 +79,7 @@ Owner request: audit the course, fact-check, add sources, knowledge and exercise
 - Not done: a human playing the games; the tab-switch fix is covered by stream tests only.
 
 ## Open follow-ups (added)
-- Changes are uncommitted in the working tree.
+- (Committed later the same day; see the end of this file.)
 - `Check.fs` is not in `fsharp/web/Web.fsproj` (not needed in the browser).
 - A turn queue (honouring Up-then-Left within one step) is still only a question in Module 3.
 - Resolved from the earlier list: backwards `Time` is now harmless behind `clampTime`.
@@ -123,7 +123,7 @@ Owner approved eleven extensions; spec: `docs/superpowers/specs/2026-11-11-cours
 - VS Code's own display of the JS type errors was not checked, only `tsc`.
 - TypeScript version is not pinned (`TS_PACKAGE` can pin it).
 - Scala lacks the JS test "play without a best answers LoadBest with 0".
-- Everything is uncommitted in the working tree.
+- (Committed later the same day; see the end of this file.)
 
 ## Playwright end-to-end suite (2026-11-11, owner's suggestion; spec Item 12)
 - `e2e/` (own `package.json`, `@playwright/test` 1.65.0 pinned) and `scripts/e2e.sh`; `scripts/play.mjs` deleted, `smoke.mjs` kept. The course tracks stay dependency-free.
@@ -131,3 +131,9 @@ Owner approved eleven extensions; spec: `docs/superpowers/specs/2026-11-11-cours
 - Result: 176 tests pass in about 20 s. No frame of any track differs from the model.
 - Found and fixed: the three tracks read an unusual stored best differently (`"1e2"`, `"7.0"`, `"2147483648"`). Ruling: only plain decimal digits with a value of at most 2147483647 count; anything else reads as 0. Applied to `js/solutions/browser.js`, `scala/web/BrowserPlatform.scala`, `fsharp/web/BrowserPlatform.fs`.
 - Still not covered: real animation timing and real hidden-tab throttling (the clamp is tested with a fake 10 s frame), rendered pixels and fonts, zoom, touch, key auto-repeat, Firefox (no build installed), and a person playing.
+
+## Wrap-up (2026-11-11)
+- `docs/contract.md` is now the canonical contract; the "contract" section of the 2026-10-28 plan is superseded.
+- Specs: `specs/2026-11-11-audit-pass.md` (written after the fact) and `specs/2026-11-11-course-extensions.md` (twelve items, marked as built).
+- Committed on branch `audit-and-extensions` (`edd57f0`), merged into `main` (`c67d81b`) and pushed to origin on the owner's instruction.
+- `docs/HANDOFF.md` is the starting point for the next maintainer; `notes/2026-11-11-session-log.md` records the day.