Add Last Update widget to Homepage via record-update script

record-update parses nvd diff after switch and writes latest.json;
Homepage polls a local-only nginx listener and renders date/changes/
closure/kernel via a customapi widget.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/record-update.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# Parse `nvd diff <old> <new>` output and write a JSON summary
+# consumed by the Homepage dashboard's customapi widget.
+set -euo pipefail
+
+OLD="${1:-}"
+NEW="${2:-/run/current-system}"
+OUT_DIR="/var/lib/homepage-updates"
+OUT_FILE="$OUT_DIR/latest.json"
+
+if [ -z "$OLD" ]; then
+  echo "usage: record-update <old-system> [new-system]" >&2
+  exit 1
+fi
+
+mkdir -p "$OUT_DIR"
+
+DIFF=$(nvd diff "$OLD" "$NEW" 2>&1 || true)
+
+CHANGES=$(printf '%s\n' "$DIFF" | grep -cE '^\[[UAR][.*]\]' || true)
+CLOSURE=$(printf '%s\n' "$DIFF" | grep -oE 'disk usage [+-][0-9.]+[A-Za-z]*B?' | head -1 | sed 's/disk usage //')
+CLOSURE="${CLOSURE:-+0B}"
+
+KERNEL=$(uname -r)
+DATE=$(date '+%Y-%m-%d %H:%M')
+
+if [ "$CHANGES" = "0" ]; then
+  LABEL="No changes"
+else
+  LABEL="$CHANGES package changes"
+fi
+
+cat > "$OUT_FILE.tmp" <<EOF
+{
+  "date": "$DATE",
+  "changes": "$LABEL",
+  "closure": "$CLOSURE",
+  "kernel": "$KERNEL"
+}
+EOF
+mv "$OUT_FILE.tmp" "$OUT_FILE"