feat: extraction coverage — message-granular ledger + token-batched runs (d132373 vision)

THE MESSAGE IS THE UNIT OF COVERAGE (vision-extraction-coverage.md): a
per-chat append-only ledger (coverage.jsonl) records which messages the
pipeline has extracted, by content fingerprint over exactly what the
extraction view sees (one shared line builder — core/coverage.ts); the
uncovered remainder is DERIVED at read time, never dual-tracked. A quiz
answer merging into the asking message re-opens only that message;
plan-block data-part attach never re-opens anything.

- The trigger (turn-service) replaces every-3-quiz-answers with
  uncovered-tokens >= EXTRACTION.chunkTokens (4096) — quiz-less sessions
  extract too, content size is the honest signal.
- runExtraction is now chunked: token-budgeted batches of the oldest
  uncovered consecutive messages (a tool call + result never split), each
  merged batch checkpointing its messages' coverage atomically — an abort
  or error loses at most the in-flight batch; merged batches stay covered.
- Observation refs are batch-tagged (obs:<batchTag>:<sourceId>): re-runs
  of the same batch dedupe; a re-opened message's fresh understanding
  lands as a new event. Fixes the old obs:p1 position-collision.
- New API: GET /api/graph/coverage (exact per-session derived coverage +
  running flags, most-uncovered first) and POST /api/graph/coverage/extract
  (manual run for one session, 409 while in flight).
- Graph view chrome: the coverage button opens a panel with every
  session's covered/uncovered tokens and a per-session Extract button —
  the manual answer to aborted runs, errors, and dormant tails. Renders
  even when the graph is empty: an empty graph with uncovered sessions is
  exactly when it matters. Polls only while open.
- Notes imports keep the whole-file checkpoint path (coverage undefined).
- Tests: pure-core coverage suite (11), chunked-pipeline suite (3:
  multi-batch + no-op, abort-keeps-earlier-batches + remainder re-run,
  re-open alone + data-part invisibility), panel render suite (5);
  pendingQuizAnswers and its tests deleted as dead code. 486/486.

Live-smoked on real GLM: manual extract of "teach me modal realism" ran
one batch, wrote 4 coverage entries, panel flipped to "1.3k covered ·
complete" with the button disabled, graph refetched (nodes 11), usage
persisted with real stats.

app/api/graph/coverage/extract/route.ts

@@ -0,0 +1,36 @@
+/**
+ * POST /api/graph/coverage/extract — the manual extraction affordance
+ * (vision-extraction-coverage.md): run the pipeline over ONE session's
+ * uncovered content, whatever its size — the user's answer to an aborted
+ * run, a pipeline error, or a session that went dormant under the chunk
+ * budget. The pipeline itself batches under EXTRACTION.chunkTokens and
+ * checkpoints coverage per merged batch, so this is the same run the
+ * trigger fires, just user-initiated. 409 while a run is already in
+ * flight (the dock is the source of truth for that); failures are logged
+ * by the pipeline and leave coverage untouched — the button stays honest.
+ */
+import { extraction, extractionStatuses } from "@/src/server";
+
+export const dynamic = "force-dynamic";
+
+export async function POST(request: Request) {
+	let body: unknown;
+	try {
+		body = await request.json();
+	} catch {
+		return Response.json({ error: "Invalid JSON body" }, { status: 400 });
+	}
+	const chatId = (body as { chatId?: unknown }).chatId;
+	if (typeof chatId !== "string" || chatId === "") {
+		return Response.json({ error: 'Body must be {chatId: string}' }, { status: 400 });
+	}
+	if (extractionStatuses().some((run) => run.kind === "chat" && run.chatId === chatId)) {
+		return Response.json({ error: "An extraction run is already in flight for this session" }, { status: 409 });
+	}
+	// Fire-and-forget, like the trigger: the dock + the coverage panel's
+	// running flags track progress; the promise never blocks the response.
+	void extraction.runExtraction(chatId).catch((err: unknown) => {
+		console.error(`[chat ${chatId}] manual extraction failed:`, err);
+	});
+	return Response.json({ started: true }, { status: 202 });
+}