Add an end_turn field to tools

[jlowin]

Enhancement Description

Generally, when an agent uses a tool we need to show it the result. However, for some tools we know the turn should end -- almost all builtin tools work this way (like marking a task successful). However, today they must issue the EndTurn event before the ToolResult event. By adding a flag to the tool, the tool call handler could emit the end turn event automatically.

Use Case

No response

Proposed Implementation

No response