Server side: writeData() now takes a message, and each action in the
POST handler computes its own — e.g. "admin: add idea "Title"", "admin:
clear note on slug". For setTodos (which ships the whole blob), diff
old vs new per slug to produce messages like "neighbor-sum-avoidance:
add T6" or "mark T1 done, add T5".
Client side: syncFromServer() falls back to the bundled admin-data.json
when /api/admin is unreachable, so the admin panel reflects committed
state under `astro dev` (which doesn't run Netlify Functions).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
e7dd3ed8eb