fix(m2-harness): add McNemar cc/midp aliases, fix replication ELEVATE gate (positive lift only), support pretty-JSON parsing

- mcnemarFull: add cc (=continuityCorrected) and midp (=midP) aliases for VAL-HARNESS-005/006 probes; legacy scalar mcnemar(8,2)~0.114 unchanged
- verdict(): ELEVATE now requires delta_pp>=5 (positive lift, NEVER Math.abs); negative replicated delta yields NO-LIFT, not ELEVATE
- parseResultsFile(): accept pretty-JSON objective-runner schema (delta_pp/mcnemar_p/significant) in addition to JSONL
- Tests: stats.test.js (alias+legacy fields) + replication.test.js (ELEVATE gate, negative-delta, pretty-JSON parsing)