verify(P3): dead-code-and-stale-prefix-cleanup — 4-layer verify PASS + ship

VERIFY: structural — dead export + stale comments + prefixes gone; behavioral — 616 tests + CI PASS; quality — env-override test updated.

---ci---
project: acdl
phase: 3
milestone: v1.16
status: complete
phase_role: execution
requirements:
  covered: [REQ-167]
  partial: []
---/ci---

tests/test_deploy_workflow_env_input.py

@@ -78,6 +78,7 @@ def test_run_platform_sh_has_environment_flag():
     text = (ROOT / "scripts" / "run_platform.sh").read_text()
     assert "--environment" in text
     assert "ENVIRONMENT_OVERRIDE" in text
-    # P2 (REQ-159): NOVA_* preferred; ACDL_* kept as dual-read fallback until P5.
+    # P3 (REQ-167): NOVA_* only; the dead ACDL_ENVIRONMENT_OVERRIDE export
+    # (comment said "removed in P5" but the line was present) is gone.
     assert "NOVA_ENVIRONMENT_OVERRIDE" in text
-    assert "ACDL_ENVIRONMENT_OVERRIDE" in text  # legacy fallback, removed in P5
+    assert "ACDL_ENVIRONMENT_OVERRIDE" not in text