chore(quickjs): disallow task as a configurable ptc tool (#606)

### Summary

The code interpreter now comes with a global `task` tool out of the box.
As a result, we should disallow specifying the `task` tool for ptc. This
PR implements logic that forbids the task tool as in ptc and throws with
a detailed error message if found. This PR also updates the RLM agent
example and READMEs.

### Tests

Unit tests validating expected behavior for task by name and tool
instance with "task" name.