Cost channel cull: the cluster-naming fold dies — two stages, two channels

Off UI's d651f93 flag (displayCostTotals already isolates the display to
extraction + audit; the naming stage row and naming runs were filtered
out client-side). This culls the server side of the same ruling.

THE STANDING RULING, REVERSED BY ITS OWN PREMISE: NamingRunUsage /
readNamingRuns / appendNamingUsage were kept at the wave-7 namer kill
ONLY because cost-summary's HISTORICAL naming stage read them. With the
fold culled, that premise dies — so the whole ledger read path goes too,
following the wave-7 embeddings precedent chain: consumer-less ledger
seams are deleted, and the on-disk naming-runs.jsonl stays INERT (real
trees keep their historical spend bytes; they are simply not displayed
anywhere — the same treatment as historical stages.embedding spend).

- core/cost-summary.ts: two channels in (chat + notes front doors), two
  stages out; RecentRun.kind collapses to "extraction" (labels field
  gone); CostSummaryInput.naming gone; totalDollars = extraction + audit.
- ports/store/contracts/config: appendNamingUsage + readNamingRuns ports,
  store impls + guards, the NamingRunUsage interface, and
  LEDGER_FILES.namingRuns die. graphRevision no longer counts the file
  (a smaller revision value is harmless — reads never compare).
- components/graph-view.tsx (mechanical, flagged): the defensive
  .filter(run.kind !== "naming") guards a kind that no longer exists.
- Tests: cost-summary's both-channels fold pins; the naming fixtures and
  the appendNamingUsage store pin die with the seams.

src/core/contracts/graph.ts

@@ -79,27 +79,6 @@ export interface NamingRunStats {
 	appended: number;
 }
 
-/** One cluster-naming run's usage record — the money channel's THIRD stage
- *  (graph cost metrics, 2026-09). The namer is graph-global (tied to no
- *  chat or source), so runs live in their own append-only ledger
- *  (config.LEDGER_FILES.namingRuns). Appended when a run actually called
- *  the model; skipped refreshes (nothing to name) never bill and never
- *  append. Idempotent per startedAt — same discipline as every usage
- *  channel. Cost is INFERRED at read time from steps + model
- *  (core/prices.ts) — dollars are never stored. */
-export interface NamingRunUsage {
-	/** ms epoch — the idempotency key. */
-	startedAt: number;
-	/** ISO — wall-clock time of the run. */
-	at: string;
-	durationMs: number;
-	/** The naming run's labeler role model id (the role died in wave 7;
-	 * the field stays as the historical record's shape). */
-	model: string;
-	/** Every billed call (usually ONE — the namer is single-submit). */
-	steps: CallUsage[];
-	stats: NamingRunStats;
-}
 
 export interface GraphNode {
 	/** Opaque stable id, store-assigned: "n_" + nanoid-like. */