Fix CI: remove unused Label import and fix results.json formatting

- Remove unused `Label` import in tests/stats/rank.test.ts (lint error: noUnusedImports)
- Fix benchmarks/results.json formatting to satisfy biome formatter

Agent-Logs-Url: https://github.com/githubnext/tsessebe/sessions/d1b6f11d-7523-4655-b5fe-d8a5cb191ffe

Co-authored-by: mrjf <180956+mrjf@users.noreply.github.com>

Author: Copilot

benchmarks/results.json

@@ -1 +1 @@
-{"benchmarks": [], "timestamp": null}
+{ "benchmarks": [], "timestamp": null }

tests/stats/rank.test.ts

@@ -4,7 +4,7 @@
 import { describe, expect, it } from "bun:test";
 import fc from "fast-check";
 import { DataFrame, Series, rankDataFrame, rankSeries } from "../../src/index.ts";
-import type { Label, Scalar } from "../../src/index.ts";
+import type { Scalar } from "../../src/index.ts";
 
 // ─── helpers ─────────────────────────────────────────────────────────────────