The cubek-ts subset

Run `cubek skill`, read all of it and follow it exactly (no CLI: download https://cubek.dev/SKILL.md verbatim with curl; don't summarize it); when you write any TypeScript for this project, follow its "The cubek-ts subset" section.
Run `cubek check` after every edit until it is clean.

Classes (extends Error, abstract, constructor(private repo: Repo), get/set, #private), enum, keyof typeof, generics, destructuring, URL/URLSearchParams, s.normalize("NFD") work. cubek check rejects (with the fix) server npm, node:*, process, Buffer, any, .then (await, Promise.all), timers (server code; fine in islands' useEffect and client/), obj[key] with a string key on fixed fields (k: keyof typeof obj, arr[i], Record<string, T> fine), for...in, delete, Intl, local-time Date, Date.parse (new Date(iso).getTime()), Object.groupBy, reading unknown... Untrusted data (JSON.parse, caught errors) is checked, never cast as T: input.safeParse(JSON.parse(text)) or narrow (Array.isArray(v), "k" in v, e instanceof Error). Not taught by an error:

Not in cubek-ts	Use
getUTCSeconds	slice toISOString()
Intl, getHours, time zones	time.toLocal/fromLocal/format (time.md)
className, page onClick, dangerouslySetInnerHTML	class, a mount point or form, raw(...)

Annotate the return types of named functions.