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/raf.js

@@ -0,0 +1,28 @@
+// Ported from nanoraf 3.1.0 (MIT) — https://github.com/choojs/nanoraf
+// Only call requestAnimationFrame when needed.
+
+import { ok, equal } from './assert.js'
+
+export default function nanoraf (render, raf) {
+  equal(typeof render, 'function', 'nanoraf: render should be a function')
+  ok(typeof raf === 'function' || typeof raf === 'undefined', 'nanoraf: raf should be a function or undefined')
+
+  if (!raf) raf = globalThis.requestAnimationFrame
+  let redrawScheduled = false
+  let args = null
+
+  return function frame (...frameArgs) {
+    if (args === null && !redrawScheduled) {
+      redrawScheduled = true
+
+      raf(function redraw () {
+        redrawScheduled = false
+        const _args = args
+        args = null
+        render(..._args)
+      })
+    }
+
+    args = frameArgs
+  }
+}