Graph pipeline cost metrics: capture naming spend, fold all channels, cost pill + panel

- Cluster namer bills the money channel now: per-step usage + model
  captured via onStep, persisted as NamingRunUsage records to
  data/graph/naming-runs.jsonl (idempotent per startedAt; failed/aborted
  runs persist too — money spent either way). callUsage promoted to
  extraction.ts module scope for reuse.
- core/cost-summary.ts: the pure fold behind the pill — chat runs,
  notes-source runs, and naming runs into stage totals (extraction /
  audit / naming) + newest-first recent runs. Dollars INFERRED read-time
  via prices.ts, never stored; unpriced models excluded-but-counted
  (render '—', never a silent zero); tokens always sum.
- GET /api/graph/costs (src/server graphCosts composition, thin route).
- Graph view: bottom-left cost pill (cumulative dollars headline) +
  expandable breakdown panel (stage rows with tokens secondary, recent
  runs with time/title/merged/cost); fetched on mount, refetched when a
  pipeline run finishes; merged into one bottom-left stack with the
  running-pipeline pills.
- Tests: pure-fold suite, naming capture wiring (full importNotes ->
  naming path), store idempotency + strict reads.

src/server/graph.ts

@@ -1,4 +1,6 @@
 import type { GraphSnapshot } from "../core/contracts.ts";
+import type { GraphCostSummary } from "../core/cost-summary.ts";
+import { graphCostSummary } from "../core/cost-summary.ts";
 import { graphSnapshot } from "../core/graph.ts";
 import { stores } from "./stores.ts";
 
@@ -11,3 +13,25 @@ import { stores } from "./stores.ts";
 export function graphView(): GraphSnapshot {
 	return graphSnapshot(stores);
 }
+
+/** The graph view's cost surface (GET /api/graph/costs — the 2026-09 cost
+ *  pill): fold every usage channel into stage totals + recent runs. A pure
+ *  read over the chat records (chat-front-door runs), the notes sources
+ *  (notes-front-door runs), and the naming ledger (graph-global runs);
+ *  dollars are inferred by the pure core fold (core/cost-summary.ts +
+ *  prices.ts) — nothing here stores or caches money. */
+export function graphCosts(): GraphCostSummary {
+	const chats = stores.chatStore
+		.listChats()
+		.flatMap((summary) => {
+			const record = stores.chatStore.getChat(summary.id);
+			return record?.extractions?.length
+				? [{ title: record.title ?? summary.id, extractions: record.extractions }]
+				: [];
+		});
+	const sources = stores.graphStore
+		.readSources()
+		.filter((s) => s.extractions?.length)
+		.map((s) => ({ filePath: s.filePath, extractions: s.extractions! }));
+	return graphCostSummary({ chats, sources, naming: stores.graphStore.readNamingRuns() });
+}