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---

.github/workflows/release.yml

@@ -1,4 +1,4 @@
-# ACDL Release Pipeline — GitHub Actions (production)
+# Nova Release Pipeline — GitHub Actions (production)
 #
 # Runs on push to main. Computes the next semver tag from the latest tag +
 # commit history, creates the tag, updates floating MAJOR.MINOR and MAJOR tags,
@@ -8,7 +8,7 @@
 #   - Regular phase commit -> bump PATCH (v1.6.0 -> v1.6.1)
 #   - Milestone completion ("docs(milestone): complete") -> bump MINOR (v1.6.1 -> v1.7.0)
 #   - Major bumps are manual (not implemented here).
-name: acdl-release
+name: nova-release
 
 on:
   push:
@@ -87,6 +87,6 @@ jobs:
             BODY=$(git log --format='- %s' HEAD)
           fi
           gh release create ${{ steps.version.outputs.new_tag }} \
-            --title "ACDL ${{ steps.version.outputs.new_tag }}" \
+            --title "Nova ${{ steps.version.outputs.new_tag }}" \
             --notes "$BODY" \
             --generate-notes || true