core-extraction: buildJsonReport's dailyMap fallback is unreachable dead code #1067

Found during #929 review: buildJsonReport in packages/cli/src/main.ts takes durable from both call sites unconditionally (buildDurablePeriod() never returns null), so the dailyMap fallback branch (~30 lines) can never execute and cannot be covered by any test from any entry point. #929 originally patched this dead branch for the midnight-straddle rule; the hunk was dropped as unreachable. Follow-up: make durable a required parameter and delete the fallback branch (tsc + suite will prove nothing depends on it), or document why the fallback stays.