test(keyviz): replace fixed sleep with eventually in TestHotKeysAggregatorRaceFree

CI flake observed on Actions run 26765510693 (PR #902 branch but
unrelated to that PR -- the keyviz/ change is on main and surfaced
there by chance):

  --- FAIL: TestHotKeysAggregatorRaceFree (0.11s)
      hot_keys_test.go:356: Expected value not to be nil.

Root cause: same wall-clock racing pattern as the SQS-throttle and
Redis-TTL flake series (PR #891, #903). The test:

  1. Launches an aggregator goroutine (Step=5ms tick).
  2. Spawns 8 workers each calling Observe 500 times.
  3. Sleeps 50ms.
  4. Asserts both per-route snapshots are non-nil.

The aggregator publishes a snapshot only on a tick (or on ctx-done
drain). Under -race on a slow CI runner, the Run goroutine itself
can be slow to schedule -- the 50ms wait may not contain a single
actual tick worth of scheduler time, so hotKeysSnap stays at its
initial nil atomic.Pointer load and the assertion fires.

Fix: require.Eventually with a 3-second budget + 5ms poll cadence,
asserting both snapshots non-nil. The test still pins the load-bearing
property (snapshot reads are lock-free; the atomic.Pointer.Load works
without contention with the publisher); only the WAIT mechanism
changes from "sleep blindly and hope" to "poll until ready or fail".
Total time bound is at most 3 s on a slow runner, ~5-50 ms in the
common case.

Validation:
  go test ./keyviz/ -run TestHotKeysAggregatorRaceFree -race -count=5 -> ok 1.1s
  gofmt + golangci-lint -> 0 issues

Caller audit: test-only file; no Go callers affected. The flake
linage matches the structural fixes in PR #891/#903 (replace
fixed-time-window sleep with require.Eventually); future flakes
in this category should follow the same pattern.

Author: bootjp

keyviz/hot_keys_test.go

@@ -348,13 +348,19 @@ func TestHotKeysAggregatorRaceFree(t *testing.T) {
 		}(w)
 	}
 	wg.Wait()
-	// Let the aggregator drain + publish a few ticks.
-	time.Sleep(50 * time.Millisecond)
-	// Snapshot reads must be lock-free and consistent.
-	s1 := s.HotKeysSnapshot(1)
-	s2 := s.HotKeysSnapshot(2)
-	require.NotNil(t, s1)
-	require.NotNil(t, s2)
+	// Wait for the aggregator to drain the queue and publish at least
+	// one tick-driven snapshot for each route. The previous
+	// time.Sleep(50ms) raced the aggregator's tick (Step=5ms) on slow
+	// -race CI runners — the Run goroutine could be slow to schedule
+	// at all, leaving hotKeysSnap as its initial nil atomic.Pointer
+	// load by the time the assertions fired. require.Eventually with
+	// a 3-second budget + 5ms poll cadence rides out any scheduler
+	// jitter; snapshot reads themselves remain lock-free
+	// (atomic.Pointer.Load), which is what this test pins. Observed
+	// failure: Actions run 26765510693.
+	require.Eventually(t, func() bool {
+		return s.HotKeysSnapshot(1) != nil && s.HotKeysSnapshot(2) != nil
+	}, 3*time.Second, 5*time.Millisecond, "aggregator must publish a snapshot for each route within the budget")
 	cancel()
 	wgRun.Wait()
 }