Status: Completed Task 4.
Commit: 821ea8e39 (`feat(stats): write realtime mileage candidates`).
Test Summary: `go test ./internal/stats -run TestWriterAppendWritesSourceCandidateAndProjection -count=1` (PASS) and `go test ./internal/stats -count=1` (PASS).
Concerns: `Writer.Append` now always runs projector projection per sample event, even when source identity is unavailable; this preserves final row refresh behavior and matches existing schema flow.
Files changed: `go/vehicle-gateway/internal/stats/daily_metric.go`, `go/vehicle-gateway/internal/stats/daily_metric_test.go`.
Report path: `.superpowers/sdd/task-4-report.md`.