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/core/ports.ts

@@ -28,6 +28,7 @@ import type {
 	TurnUsage,
 	NotesSource,
 	ClusterLabeling,
+	NamingRunUsage,
 	EmbeddingsLedger,
 } from "./contracts.ts";
 import type { UserSettings } from "./settings.ts";
@@ -101,6 +102,11 @@ export interface GraphStore {
 	appendClusterLabel(labeling: ClusterLabeling): void;
 	readClusterLabels(): ClusterLabeling[];
 
+	/** Append one cluster-naming run's usage (graph-global money channel) —
+	 *  idempotent per startedAt. */
+	appendNamingUsage(entry: NamingRunUsage): void;
+	readNamingRuns(): NamingRunUsage[];
+
 	/** Upsert one imported-notes source record (config.SOURCES_FILE — a
 	 *  JSON map, not a ledger; an upsert keeps the existing usage log). */
 	upsertSource(source: NotesSource): void;