tools: add update-star-chart.sh to regenerate the README star chart

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tools/update-star-chart.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+# Regenerate assets/star-history.png from the repo's own star data.
+# Needs a gh login with admin/collab access to the repo (GitHub restricted
+# the stargazers API to admins/collaborators in June 2026), plus matplotlib.
+set -e
+cd "$(dirname "$0")/.."
+
+gh api -H "Accept: application/vnd.github.star+json" --paginate \
+  "repos/OpenClaudia/openclaudia-skills/stargazers?per_page=100" \
+  --jq '.[].starred_at' > /tmp/openclaudia-stars.txt
+
+python3 - <<'EOF'
+import matplotlib
+matplotlib.use('Agg')
+import matplotlib.pyplot as plt
+from datetime import datetime
+
+dates = sorted(datetime.strptime(l.strip(), '%Y-%m-%dT%H:%M:%SZ')
+               for l in open('/tmp/openclaudia-stars.txt'))
+fig, ax = plt.subplots(figsize=(8, 4.5), dpi=150)
+ax.plot(dates, range(1, len(dates) + 1), color='#2f81f7', linewidth=2)
+ax.fill_between(dates, range(1, len(dates) + 1), alpha=0.1, color='#2f81f7')
+ax.set_title('OpenClaudia/openclaudia-skills — Star History', fontsize=12)
+ax.set_ylabel('GitHub Stars')
+ax.grid(alpha=0.3)
+fig.autofmt_xdate()
+fig.tight_layout()
+fig.savefig('assets/star-history.png')
+print(f'{len(dates)} stars')
+EOF
+
+sed -i '' -E "s/<sub>Updated [0-9]{4}-[0-9]{2}-[0-9]{2}\./<sub>Updated $(date +%F)./" README.md
+rm -f /tmp/openclaudia-stars.txt