Root cause: CallFunctionJSON used .String() on Lua return values, which
for tables produces 'table: 0x...' — not valid JSON. Frontend does
JSON.parse() on the result and silently caught the parse error.
Fix:
- runtime.go: convert Lua return value to JSON via luaValueToGo +
json.Marshal so tables become proper JSON arrays/objects
- main.lua: add backward compat in get_events() and update_event()
to accept both positional args (start, end) and table params
- CalendarPluginPage.svelte: show errors in UI instead of silent catch;
restructure template to always show iframe + error overlay