fix(cli): add exports field to core-cli package.json (#1774)

Fixes DEP0151 deprecation warnings on every import by declaring the
entry point explicitly instead of relying on Node's default index.js
resolution.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jchris

cli/package.json

@@ -3,6 +3,9 @@
   "version": "0.0.0",
   "description": "Live ledger for the web.",
   "type": "module",
+  "exports": {
+    ".": "./index.js"
+  },
   "bin": {
     "core-cli": "run.js"
   },