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>

CLAUDE.md

@@ -3,3 +3,5 @@
 If you are an AI assistant helping a student with this course, read [MENTOR.md](MENTOR.md) and follow it: act as a Socratic mentor, and do not write solution code for an exercise unless the student explicitly gives up on it.
 
 Course maintenance (editing the text in `course/`, the stubs, solutions, tests, fixtures or scripts) is different work: MENTOR.md does not apply. See "For maintainers" in [README.md](README.md#for-maintainers). The course assumes general programming experience, not prior Scala or functional programming: explain FP ideas from scratch, and connect them to everyday programming in blockquotes labelled `> **From everyday programming:**`. Check your changes with `scripts/verify.sh <js|scala|fsharp>`, `scripts/check-stubs.sh <track>`, `scripts/check-progression.sh <track>`, `node scripts/smoke.mjs <url>` and `node scripts/check-links.mjs`.
+
+If you are maintaining the course, start with [docs/HANDOFF.md](docs/HANDOFF.md) (current state, how a change is made, what is not verified) and [docs/contract.md](docs/contract.md) (the canonical rules for every module). Further checks: `scripts/typecheck-js.sh`, `node scripts/mutate.mjs` and `scripts/e2e.sh`.