docs(P00): validate specification — v1.21 milestone (REQ-245..253)

Add v1.21 requirements section (Nova Deck Refinement & Pipeline Hardening):
REQ-245 deck rename + restructure; REQ-246 thesis rename + reframe;
REQ-247 strategic-docs sync (integration objective); REQ-248 RACI
restructure (QE + SRE); REQ-249 Atelier split; REQ-250 pipeline hardening
(Checkov before plan, Wiz-or-Checkov on plan); REQ-251 theme CSS fix +
footer cleanup; REQ-252 global citation/badge/version removal; REQ-253
render + verify + ship.

Set active_milestone=v1.21 in config.json. Sync PROJECT.md strategic-
direction pillar for the integration objective (Objective #4 reframed),
deterministic-trust reword (Objective #2), CTO-grade ROI metrics
(Objective #3), and anti-goal updates.

---ci---
project: acdl
phase: 0
milestone: v1.21
status: specify
---/ci---

.ciagent/config.json

@@ -8,7 +8,7 @@
   ],
   "active_project": "acdl",
   "active_projects": ["acdl"],
-  "active_milestone": "v1.20",
+  "active_milestone": "v1.21",
   "autonomy": {
     "level": "full",
     "escalation_hooks": ["deploy", "delete_data", "merge_to_main"],