docs(milestone): complete v1.15 — Nova Rebrand (tag v1.15.4)

P5 final-review-ship complete: dual-read fallback removed (REQ-164) —
core/env.py NOVA-only, .env.secrets load paths NOVA-only (G-106 retired),
nova_tagging.py hard-fails any acdl:* tag, legacy ACDL_* Gitea secrets
deleted, ACDL_LIFECYCLE_MODE/ACDL_LOCAL_TIER/ACDL_HITL_* exports removed
from scripts, SNS subject → Nova SoD halt (P1-2), bootstrap scripts
NOVA-only. Review: 2 P0 auto-fixed (duplicate delenv), P1-1/P1-2 resolved,
doc-drift fixed. Audit: tags v1.15.0-4 exist; traceability REQ-155..164
all complete; ARCHITECTURE naming table matches codebase. 615 pytest PASS;
run_ci.sh 3-stage PASS. NOVA_MIGRATION.md marked COMPLETE.

---ci---
project: acdl
phase: 5
milestone: v1.15
status: complete
phase_role: final
requirements:
  covered: [REQ-155, REQ-156, REQ-157, REQ-158, REQ-159, REQ-160, REQ-161, REQ-162, REQ-163, REQ-164]
  partial: []
---/ci---

.ciagent/CHECKPOINT.json

@@ -1,11 +1,11 @@
 {
-  "phase": 4,
+  "phase": 5,
   "stage": "complete",
   "milestone": "v1.15",
-  "phase_role": "execution",
+  "phase_role": "final",
   "attempts": 0,
-  "updated_at": "2026-07-30T00:10:00Z",
-  "milestone_complete": false,
-  "requirements": ["REQ-163"],
+  "updated_at": "2026-07-30T00:11:00Z",
+  "milestone_complete": true,
+  "requirements": ["REQ-155", "REQ-156", "REQ-157", "REQ-158", "REQ-159", "REQ-160", "REQ-161", "REQ-162", "REQ-163", "REQ-164"],
   "tag": "v1.15.4"
 }