feat(migrate): add @choojs/migrate — the choo-migrate v7→v8 codemod

Regex-based on purpose: converts simple top-level CJS patterns to ESM,
remaps package specifiers to their @choojs homes, points retired nano*
packages at built-in replacements (choo-lazy-route → lazy()), and reports
everything it refuses to guess at instead of guessing. Validated against
choo's own v7 example app: migrated output runs on v8 unmodified.

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

packages/migrate/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "@choojs/migrate",
+  "version": "8.0.0-dev",
+  "description": "Codemod: migrate choo v7 apps to @choojs v8 (ESM, new package names)",
+  "type": "module",
+  "bin": {
+    "choo-migrate": "./cli.js"
+  },
+  "exports": {
+    ".": "./lib/transform.js"
+  },
+  "files": [
+    "cli.js",
+    "lib"
+  ],
+  "engines": {
+    "node": ">=24"
+  },
+  "repository": "choojs/choo",
+  "keywords": [
+    "choo",
+    "codemod",
+    "migration"
+  ],
+  "license": "MIT"
+}