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/ports.ts

@@ -27,7 +27,6 @@ import type {
 	SessionCheckpoint,
 	TurnUsage,
 	NotesSource,
-	NamingRunUsage,
 } from "./contracts.ts";
 import type { UserSettings } from "./settings.ts";
 
@@ -102,8 +101,6 @@ export interface GraphStore {
 
 	/** 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). */