fix(review-gates): green success badges, null-safe preview rows, optional section items

- Extract shared statusBadgeClass() helper (src/viewers/statusBadge.ts) so
  SqlViewer, CteResultViewer and PhaseSummaryViewer can't drift: ok/success/
  passed/promoted render green (--success), warn renders amber (--warning),
  error/failed stay destructive red, everything else stays neutral outline.
  Previously CteResultViewer/PhaseSummaryViewer mapped "ok"/"promoted" to the
  default badge variant, which is bg-primary (GSD red) — success states
  rendered red.
- enrich.js: buildCteResultV2 now falls back preview.rows to [] instead of
  null when last_test.preview_rows is missing (pre-upgrade ok records), and
  CteResultViewer reads result.preview?.rows?.length with a null-safe
  fallback so it degrades to the "No preview rows" empty state instead of
  crashing.
- PhaseSummaryViewer: section.items is optional (model-authored sections can
  be prose-only); render (section.items ?? []) instead of crashing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

harness/.pi/extensions/gate/enrich.js

@@ -85,7 +85,7 @@ function buildCteResultV2(thinData, cteInfo) {
 		warnings: lt.warnings || [],
 		sql_hash: lt.sql_hash,
 		columns: (lt.columns || []).map((name) => ({ name, description: "" })),
-		preview: { columns: lt.columns || [], rows: lt.preview_rows || null },
+		preview: { columns: lt.columns || [], rows: lt.preview_rows || [] },
 		note: thin.note,
 	};
 }