feat(core): add @choojs/core — ESM port of choo with consolidated nano* internals

Same public API as choo 7.1.0 (use/route/start/mount/toString/emit; choo()
callable with or without new, Choo exported). nanobus, nanorouter+wayfarer,
nanolru+component cache, nanoraf, nanohref, nanotiming, document-ready and
scroll-to-anchor are ported into lib/ with per-file attribution; nanoquery
is replaced by URLSearchParams. The v7 node test suite is ported from tape
to node:test and passes unchanged in behavior.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014NgfSjHE11oFpoSnLVKLXd

packages/core/lib/dom.js

@@ -0,0 +1,25 @@
+// Ported from document-ready 2.0.1 and scroll-to-anchor 1.0.0 (MIT)
+// https://github.com/bendrucker/document-ready — https://github.com/yoshuawuyts/scroll-to-anchor
+
+import { notEqual } from './assert.js'
+
+export function documentReady (callback) {
+  notEqual(typeof document, 'undefined', 'documentReady only runs in the browser')
+  const state = document.readyState
+  if (state === 'complete' || state === 'interactive') {
+    return setTimeout(callback, 0)
+  }
+
+  document.addEventListener('DOMContentLoaded', function onLoad () {
+    callback()
+  })
+}
+
+export function scrollToAnchor (anchor) {
+  if (anchor) {
+    try {
+      const el = document.querySelector(anchor)
+      if (el) el.scrollIntoView(true)
+    } catch (e) {}
+  }
+}