feat(P1): Nova rebrand — docs/decks/prose/schema-$id/release-titles (REQ-155/156/157)

Rebrand ACDL/Agentic Cloud Delivery Platform → Nova across README, docs/,
decks (markdown + mermaid .mmd + HTML), pyproject.toml name/description,
schema $id URLs (acdl.cloudinit.dev→nova.cloudinit.dev), release.yml
title/workflow-name. Nova tagline added to README header + both deck title
slides + docs/vision.md (alongside existing North Star, D-106). S&P theme
untouched (D-107). New docs/NOVA_MIGRATION.md consumer guide. Data values
(env vars, resource names, tag keys, SSM/consumer paths) left for P2-P4.

---ci---
project: acdl
phase: 1
milestone: v1.15
status: execute
---/ci---

docs/index.md

@@ -1,4 +1,6 @@
-# ACDL — Agentic Cloud Delivery Platform
+# Nova
+
+> **Nova — The New Dawn of DevSecOps.** Security as a seamless enabler of fast deployments — not a bottleneck, not a "no" department.
 
 Consumers declare intent; the platform delivers safe production deployment
 through an agentic stack — automatically, safely, and with a complete audit
@@ -9,7 +11,7 @@ a configuration file, or an infrastructure module.
 
 ## Two repositories
 
-There are two kinds of repository in the ACDL model:
+There are two kinds of repository in the Nova model:
 
 - **Platform repo (this one).** The source code of the platform. It owns
   `modules/`, `adapters/`, `core/`, `schemas/`, `pipelines/`, `scripts/`,
@@ -75,4 +77,11 @@ Planned future features (no dates; tracked in the internal roadmap):
 
 - [Consumer Guide](consumer-guide) — start here if you are a consumer.
 - [Architecture](architecture) — start here if you are a platform engineer.
-- The [README](https://github.com/acdl/acdl) describes the platform repo.
+- The [README](https://github.com/nova/nova) describes the platform repo.
+
+> **Note:** The product brand is **Nova** (formerly ACDL — Agentic Cloud
+> Delivery Platform). The Gitea repository name (`continuous-intelligence/acdl`)
+> and the GitHub `uses:` reference (`acdl/.github/workflows/deploy.yml@…`)
+> are unchanged during the rebrand transition; only the product name is
+> changing. See the [Nova migration guide](NOVA_MIGRATION) for the
+> scheduled breaking changes.