feat(P1): restore S&P Global Energy theme + PPTX automation (REQ-214, REQ-228)

REQ-214: Restore the S&P Global Energy Marp style: block (from commit
ae0cb58 / v1.9.2 P45) to the unified deck. Colors: H1/H2 #D6002A (red-core),
title-slide bg #1B1B1B (grey-90) + 8px #D6002A top accent, body #1B1B1B,
blockquote border #D6002A, table headers #F0F0F0, font 'Akkurat Pro' with
web-safe fallbacks. Nova header/footer text preserved (rebrand not touched).
HTML re-rendered (229 S&P color refs confirmed).

REQ-228: scripts/render_deck.sh (HTML + PPTX render + git add) +
scripts/attach_release_asset.py (Gitea release asset upload via API). PPTX
is now a first-class committed binary (D-141, no LFS). README updated:
'PPTX not committed' → 'PPTX committed + attached'. PPTX committed (3.6 MiB,
19 slides).

---ci---
project: acdl
phase: 1
milestone: v1.18
status: execute
requirements:
  covered: [REQ-214, REQ-228]
  partial: []
---/ci---

scripts/render_deck.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# scripts/render_deck.sh — render a Marp deck to HTML + PPTX, commit both to git.
+# REQ-228 (v1.18): PPTX is now a first-class committed artifact + release attachment.
+#
+# Usage:
+#   bash scripts/render_deck.sh <deck-name>
+#   bash scripts/render_deck.sh nova-no-humans-platform
+#
+# Renders:
+#   docs/presentations/<deck-name>-marp.md → docs/presentations/<deck-name>.html (committed)
+#                                       → docs/presentations/<deck-name>.pptx (committed, binary)
+#
+# The PPTX is also attached to the current phase's Gitea release via
+# scripts/attach_release_asset.py (call separately after ship, or this script
+# will invoke it if NOVA_GITEA_RELEASE_ID is set).
+set -euo pipefail
+
+DECK="${1:?Usage: render_deck.sh <deck-name>}"
+cd "$(git rev-parse --show-toplevel)"
+
+SRC="docs/presentations/${DECK}-marp.md"
+HTML="docs/presentations/${DECK}.html"
+PPTX="docs/presentations/${DECK}.pptx"
+
+if [ ! -f "$SRC" ]; then
+  echo "ERROR: source deck $SRC not found" >&2; exit 1
+fi
+
+CHROME=""
+for c in \
+  /root/.cache/ms-playwright/chromium-1217/chrome-linux64/chrome \
+  /usr/bin/chromium \
+  /usr/bin/chromium-browser \
+  /usr/bin/google-chrome; do
+  if [ -x "$c" ]; then CHROME="$c"; break; fi
+done
+if [ -z "$CHROME" ]; then
+  echo "WARNING: no Chrome/Chromium found — skipping render (HTML/PPTX will need manual re-render)" >&2
+  exit 0
+fi
+export CHROME_PATH="$CHROME"
+
+echo "Rendering HTML → $HTML"
+npx --yes @marp-team/marp-cli@latest --allow-local-files "$SRC" -o "$HTML" 2>&1 | tail -3
+
+echo "Rendering PPTX → $PPTX"
+npx --yes @marp-team/marp-cli@latest --allow-local-files "$SRC" -o "$PPTX" 2>&1 | tail -3
+
+git add "$HTML" "$PPTX"
+echo "Staged $HTML + $PPTX for commit."
+
+if [ -n "${NOVA_GITEA_RELEASE_ID:-}" ]; then
+  echo "Attaching PPTX to Gitea release $NOVA_GITEA_RELEASE_ID..."
+  python3 scripts/attach_release_asset.py "$PPTX" "$NOVA_GITEA_RELEASE_ID" || \
+    echo "WARNING: attach failed — PPTX is still committed; attach manually."
+fi