fix: hoist $defs to the schema root for set_tasks

Refs like "#/$defs/AddTask" resolve from the document root, but
Type.Cyclic nested the $defs inside tasks.items, so the moonshot-flavored
gateway reported "$defs not found for reference". Hoist all $defs entries
to the parameter schema root and strip the synthetic $id that would change
fragment resolution. Update the regression test to pin the layout.

Bump version to 0.2.3.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pi-todo-herdr",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "description": "Hierarchical task tools for Pi with a live widget and Herdr sidebar integration.",
   "type": "module",
   "main": "./index.ts",