ivue@2.1.0 — Static() and the ivue/extras entry

ivue 2.1 adds a second package entry, ivue/extras — the toolkit
beyond the reactive core. The primary ivue entry stays the bare 1.1 kB
engine; extras are paid for only by the code that imports them.

Added

• Static() — the static-side sibling of Reactive(), for
  stateless capability classes (function bags behind a namespace's
  replaceable Class slot). It returns a subclass whose visible static
  methods bind lazily with stable identity, so a retained callback — a
  router handler, a watcher, a command — keeps working while the
  namespace slot stays swappable. The raw class is never touched, so it
  remains a clean inheritance foundation.

  import { Static } from 'ivue/extras';
  
  class $Mailer {
    static send(message: Message) {
      /* ... */
    }
  }
  
  export namespace Mailer {
    export const $Class = $Mailer; // raw — children `extends` this
    export let Class = Static($Class); // bound — you call this
  }
  
  const send = Mailer.Class.send; // detachable — `this` stays correct

  Stateful, reactive instance classes stay with Reactive() —
  Static() has no instance dimension.

Changed

• The require('ivue') path now resolves to plain CommonJS
  (dist/index.cjs); the UMD build is no longer published. Node and
  bundler consumers are unaffected — only direct script-tag usage of
  dist/index.umd.js would notice, and the ES module remains available
  on every CDN.

Measured

Core entry: 1,112 B gzipped — unchanged; ivue/extras adds
368 B, imported separately. Tests: 175, at 100% coverage on
every metric. Subpath resolution verified in both ESM and CJS from a
packed tarball in a fresh consumer repo.