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---

schemas/deploy-pipeline.schema.json

@@ -1,8 +1,8 @@
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "$id": "https://acdl.cloudinit.dev/schemas/deploy-pipeline.schema.json",
-  "title": "ACDL Central Deployment Pipeline Contract",
-  "description": "Declarative contract for the ACDL deployment pipeline. Declares the stages that run when a consumer submits a contract: validate-contract, resolve-stack, terraform-plan, checkov, confidence, apply. The platform (scripts/run_platform.sh) implements these stages. This is the declarative pipeline spec; the executable workflow is .github/workflows/deploy.yml which invokes scripts/run_platform.sh.",
+  "$id": "https://nova.cloudinit.dev/schemas/deploy-pipeline.schema.json",
+  "title": "Nova Central Deployment Pipeline Contract",
+  "description": "Declarative contract for the Nova deployment pipeline. Declares the stages that run when a consumer submits a contract: validate-contract, resolve-stack, terraform-plan, checkov, confidence, apply. The platform (scripts/run_platform.sh) implements these stages. This is the declarative pipeline spec; the executable workflow is .github/workflows/deploy.yml which invokes scripts/run_platform.sh.",
   "type": "object",
   "required": ["name", "triggers", "runner", "stages"],
   "properties": {