docs: Update agent transfer related doc string and comments

This is to address https://github.com/google/adk-python/issues/1907

PiperOrigin-RevId: 783481177

src/google/adk/flows/llm_flows/auto_flow.py

@@ -14,6 +14,8 @@
 
 """Implementation of AutoFlow."""
 
+from __future__ import annotations
+
 from . import agent_transfer
 from .single_flow import SingleFlow
 
@@ -29,19 +31,12 @@ class AutoFlow(SingleFlow):
 
   For peer-agent transfers, it's only enabled when all below conditions are met:
 
-  - The parent agent is also of AutoFlow;
+  - The parent agent is also an LlmAgent.
   - `disallow_transfer_to_peer` option of this agent is False (default).
 
-  Depending on the target agent flow type, the transfer may be automatically
-  reversed. The condition is as below:
-
-  - If the flow type of the tranferee agent is also auto, transfee agent will
-    remain as the active agent. The transfee agent will respond to the user's
-    next message directly.
-  - If the flow type of the transfere agent is not auto, the active agent will
-    be reversed back to previous agent.
-
-  TODO: allow user to config auto-reverse function.
+  Depending on the target agent type, the transfer may be automatically
+  reversed. (see Runner._find_agent_to_run method for which agent will remain
+  active to handle next user message.)
   """
 
   def __init__(self):

src/google/adk/runners.py

@@ -446,7 +446,8 @@ class Runner:
         root_agent: The root agent of the runner.
 
     Returns:
-      The agent of the last message in the session or the root agent.
+      The agent to run. (the active agent that should reply to the latest user
+      message)
     """
     # If the last event is a function response, should send this response to
     # the agent that returned the corressponding function call regardless the
@@ -475,8 +476,8 @@ class Runner:
   def _is_transferable_across_agent_tree(self, agent_to_run: BaseAgent) -> bool:
     """Whether the agent to run can transfer to any other agent in the agent tree.
 
-    This typically means all agent_to_run's parent through root agent can
-    transfer to their parent_agent.
+    This typically means all agent_to_run's ancestor can transfer to their
+    parent_agent all the way to the root_agent.
 
     Args:
         agent_to_run: The agent to check for transferability.
@@ -487,7 +488,7 @@ class Runner:
     agent = agent_to_run
     while agent:
       if not isinstance(agent, LlmAgent):
-        # Only LLM-based Agent can provider agent transfer capability.
+        # Only LLM-based Agent can provide agent transfer capability.
         return False
       if agent.disallow_transfer_to_parent:
         return False