docs: sync Haystack API reference on Docusaurus (#12091)

Co-authored-by: sjrl <10526848+sjrl@users.noreply.github.com>

Author: HaystackBot

docs-website/reference/haystack-api/agents_api.md

@@ -351,6 +351,10 @@ Process messages and execute tools until an exit condition is met.
 - "token_usage": Aggregated token usage from every LLM call in the run, summed from each LLM message's
   `meta["usage"]`.
 - "tool_call_counts": Mapping of tool name to the number of times that tool was invoked.
+- "exit_reason": Why the Agent stopped, useful for routing the output downstream (e.g. with a
+  `ConditionalRouter`). One of: `"text"` (the model returned a reply with no tool calls), the name of
+  the tool that satisfied a tool exit condition (in which case `last_message` is that tool's result),
+  or `"max_agent_steps"` (the Agent hit `max_agent_steps` before meeting an exit condition).
 - Any additional keys defined in the `state_schema`.
 
 #### run_async
@@ -399,6 +403,10 @@ if available.
 - "token_usage": Aggregated token usage from every LLM call in the run, summed from each LLM message's
   `meta["usage"]`.
 - "tool_call_counts": Mapping of tool name to the number of times that tool was invoked.
+- "exit_reason": Why the Agent stopped, useful for routing the output downstream (e.g. with a
+  `ConditionalRouter`). One of: `"text"` (the model returned a reply with no tool calls), the name of
+  the tool that satisfied a tool exit condition (in which case `last_message` is that tool's result),
+  or `"max_agent_steps"` (the Agent hit `max_agent_steps` before meeting an exit condition).
 - Any additional keys defined in the `state_schema`.
 
 ## state/state