fix(docs): scrub day-job customer name from BACKLOG.md (anti-leak gate)

Parked BACKLOG content committed in 5783b0e carried the forbidden day-job customer name at 2 sites, tripping the anti-leak gate (test_no_internal_language.py) in CI. Replaced with neutral 'second-repo' framing, preserving the held-out/calibration meaning. The gate runs in CI but not the pre-push hook -- wiring it into pre-push is a queued follow-up.

Author: Cranot

dev/BACKLOG.md

@@ -3937,14 +3937,14 @@ SUSPECTED-finding / pending rows preserved; this is the fast-lookup index.
 ### FP-quality campaign — status
 
 The detector-FP campaign on roam's own code (dogfood-found, held-out
-union-web cross-checked) closed 5 detectors this session: feature-envy
+second-repo cross-checked) closed 5 detectors this session: feature-envy
 (W1280, ~91% cut — the headline), dangerous-eval + hotspots py-eval-exec
 (the regex-bug family pair), god-components (kind-aware), vibe-check
 (rate unit fix). **Next-FP-target sampling is in flight** — the
 FP-catalogue's 3-cmd × 5-project (algo/smells/health × django/flask/
 next.js/gin/rails-or-laravel) 2-axis promotion methodology stays a
 research-track wave (#1179), not part of this burst. The ~80% / ~91% FP
-claims stay scoped to the measured roam-code + union-web cells until
+claims stay scoped to the measured roam-code + second-repo cells until
 reproduced on a 2nd language/repo (scope-claims-to-evidence-cells rule).
 
 ### Pending after this wave (queue for next session)