v0 scaffold: teacher runtime (hermetic pi SDK), data model, ledgers, normalizer

- teacher/system-prompt.md: teach methodology + quiz/ask guidelines folded in
- extensions/: quiz.ts + ask-user-question.ts (hermetic copies)
- src/teacher/create-session.ts: isolated agent (noTools builtin, own agentDir/sessions/prompt)
- src/schema.ts + ledger.ts: append-only ledgers, known-vs-understood data model
- src/extract/normalize.ts: session JSONL -> canonical doc (verified on real session)
- extractor/merger/derive/what-next: specified stubs

src/queries/what-next.ts

@@ -0,0 +1,18 @@
+/**
+ * What-next queries: territory / repairs / conversions (+ unlock-value over
+ * the expanded frontier). NOT YET IMPLEMENTED — needs the graph populated first.
+ *
+ * These run as pure traversals over the derived graph:
+ *   territory    — frontier candidates ranked by work-to-ready (missing
+ *                  requires-subtree mass), NOT fewest edges.
+ *   repairs      — weak/shaky/misconceived nodes INSIDE the held region,
+ *                  ranked by downstream load.
+ *   conversions  — missing requires-roots that would flip known-but-floating
+ *                  nodes into understood.
+ *   unlock-value — over the lazily expanded frontier, discounted by depth in
+ *                  generated territory; presented as ranked heuristic, never a number.
+ */
+
+export async function whatNext(): Promise<void> {
+	throw new Error("Not implemented — needs a populated graph (extractor + merger first).");
+}