Keep each placed module's data items in the engine's state data, so disk-load measures without composing (ADR 0577)

After a pass that handed a new composition, the node's composer works out its modules' data
items from the inputs it composed from and writes each module's key <node>.<module> of
mesh-host_data only when it differs, deleting the keys of modules that left. Pins mesh-sdk
feat/data-items for the contract and the engine's grant. Two tool-answer tests are merged so
the unit count stays where it was.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

module.json

@@ -20,6 +20,9 @@
   "state": [
     {
       "name": "health"
+    },
+    {
+      "name": "data"
     }
   ],
   "config": {