Extraction observability: usage capture, live status payload, true abort (Wave 4)

Extraction is real spend and background work; the dock needs to see
and stop it. User decisions: persist all cost data (chat record),
per-stage usage granularity, and TRUE cancellation for abort.

USAGE CAPTURE (live + persisted):
- extraction.ts: per-call onStepFinish captures each billed step's
  usage (SDK LanguageModelUsage -> CallUsage: input/output/cache
  read+write/reasoning) into the registry's live per-stage usage
  (extractor/auditor; the merger is deterministic — no model call).
- /api/graph/status runs now carry usage (model + steps per stage);
  cost/context folds are the consumer's (core/prices.ts — nothing
  stores dollars).
- ChatRecord.extractions: append-only per-run usage log (mirrors the
  turns log): startedAt key, at, durationMs, merge stats when the
  merger ran, stages. Persisted on success AND failure — a failed run
  still spent money. Idempotent per startedAt; the list payload
  (ChatSummary) never leaks it.
- EmissionStats moved to contracts/graph.ts (its contract home);
  core/graph.ts re-exports for existing importers.
- Verified end-to-end against the real pipeline (backfill one chat):
  per-step token counts, reasoning tokens, and the auditor's growing
  prompt-cache reads captured and persisted.

TRUE ABORT (the dock's abort button, user decision):
- RunningExtraction owns one AbortController per run, shared across
  phases; abortExtraction(chatId) fires it and returns whether a run
  was aborted (idempotent no-op otherwise). The pending model call
  receives the signal — the provider cancels the request, spend
  stops. throwIfAborted() at phase boundaries ends runs aborted in
  sync gaps.
- Abort is a deliberate stop, not a failure: same ledger discipline
  (nothing merged, nothing checkpointed, partial usage persisted) but
  the run reports zero emissions instead of throwing. Exported via
  src/server/observability.ts for master's /api/activity/abort route.
- Tests: mid-run abort (hanging mock that rejects on the signal),
  live-accumulation + persisted-record assertions, store-seam
  idempotency, and the summary-payload leak guard.

tests/usage.test.ts

@@ -12,7 +12,7 @@ import * as fs from "node:fs";
 import { chatStore } from "../src/store/chats.ts";
 import { PATHS } from "../config.ts";
 import { callCost, contextWindow, jobCost, sessionCost, sumSteps, turnCost } from "../src/core/prices.ts";
-import type { CallUsage, JobRecord, TurnUsage } from "../src/core/contracts.ts";
+import type { CallUsage, ExtractionRunUsage, JobRecord, TurnUsage } from "../src/core/contracts.ts";
 
 const call = (over: Partial<CallUsage> = {}): CallUsage => ({
 	inputTokens: 0,
@@ -134,3 +134,34 @@ test("appendTurnUsage: appends, is idempotent per messageId, survives saveMessag
 
 	fs.unlinkSync(`${PATHS.chats}/${record.id}.json`);
 });
+
+test("appendExtractionUsage: appends, idempotent per startedAt, not in list payload", () => {
+	const record = chatStore.createChat("extraction usage test chat");
+	const runEntry = (startedAt: number): ExtractionRunUsage => ({
+		startedAt,
+		at: "2026-09-09T00:00:00Z",
+		durationMs: 42_000,
+		stats: { nodes: 1, edges: 2, events: 3 },
+		stages: {
+			extractor: { model: "z-ai/glm-5.3-flash", steps: [call({ inputTokens: 100, outputTokens: 10 })] },
+			auditor: { model: "z-ai/glm-5.3-flash", steps: [call({ inputTokens: 50, outputTokens: 5 })] },
+		},
+	});
+	chatStore.appendExtractionUsage(record.id, runEntry(1));
+	chatStore.appendExtractionUsage(record.id, runEntry(1)); // same run appended twice → no-op
+	chatStore.appendExtractionUsage(record.id, runEntry(2)); // a retried run is a NEW spend
+	let reread = chatStore.getChat(record.id);
+	assert.equal(reread?.extractions?.length, 2);
+	// failed runs (stats absent) persist with usage — money was spent
+	chatStore.appendExtractionUsage(record.id, { ...runEntry(3), stats: undefined });
+	reread = chatStore.getChat(record.id);
+	assert.equal(reread?.extractions?.length, 3);
+	assert.equal(reread?.extractions?.at(-1)?.stats, undefined);
+
+	// the list payload must NOT leak the extractions log
+	const listed = chatStore.listChats().find((c) => c.id === record.id);
+	assert.ok(listed);
+	assert.equal("extractions" in listed, false);
+
+	fs.unlinkSync(`${PATHS.chats}/${record.id}.json`);
+});