fix: l is an ambiguous name and ruff says so (4295)

E741, run 7410. Two comprehensions in the new endpoint tests. Every other
lane was green — backend unit, frontend and integration — and nothing
published, which is the gate doing its job.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

tests/test_api_workers.py

@@ -373,7 +373,7 @@ async def test_the_stored_sample_is_what_the_page_shows(client, db, monkeypatch)
                                    "thumbnail": 0, "download": 0})
 
     body = await (await client.get("/api/system/workers")).get_json()
-    worker = next(l for l in body["lanes"] if l["name"] == "worker")
+    worker = next(r for r in body["lanes"] if r["name"] == "worker")
 
     assert worker["live"] == {
         "present": True, "replicas": 1, "pool": 4, "active": 2, "reserved": 3,
@@ -401,7 +401,7 @@ async def test_a_lane_that_stopped_answering_overwrites_its_old_reading(
     await _store_sample(db, {lane.name: wc.LaneLiveState() for lane in LANES}, {})
 
     body = await (await client.get("/api/system/workers")).get_json()
-    worker = next(l for l in body["lanes"] if l["name"] == "worker")
+    worker = next(r for r in body["lanes"] if r["name"] == "worker")
 
     assert worker["live"]["present"] is False
     assert worker["live"]["pool"] is None