fix(tool-todo): declare the unknown-key rejection in the item schema

additionalProperties stays true in the published schema while execute
rejected extra keys, so generated typings and validation disagreed with
runtime behavior. The item schema now declares additionalProperties:
false — the registry's arg validation rejects extra keys with a
path-qualified violation before execute runs — and the redundant manual
check is dropped (tool catalog regenerated).

docs/tool-catalog.md

@@ -898,7 +898,7 @@ Record and update a structured task list for the current work. Send the ENTIRE l
       "description": "The COMPLETE task list, replacing any previous list.",
       "items": {
         "type": "object",
-        "additionalProperties": true,
+        "additionalProperties": false,
         "properties": {
           "content": {
             "type": "string",