feat: Expose Gemini RetryOptions to client

google.genai SDK has introduced a new retry_options. This change exposes this configuration to ADK users Usage: ```python root_agent = Agent( model=Gemini( model='gemini-2.0-flash', retry_options=types.HttpRetryOptions( initial_delay=1, attempts=2 # ... Retry options from google.genai	),	# ... ), ``` PiperOrigin-RevId: 786472564

Author: pwwpche

src/google/adk/models/google_llm.py

@@ -22,6 +22,7 @@
 import sys
 from typing import AsyncGenerator
 from typing import cast
+from typing import Optional
 from typing import TYPE_CHECKING
 from typing import Union
 
@@ -57,6 +58,23 @@ class Gemini(BaseLlm):
 
  model: str = 'gemini-1.5-flash'
 
+ retry_options: Optional[types.HttpRetryOptions] = None
+ """Allow Gemini to retry failed responses.
+
+ Sample:
+ ```python
+ from google.genai import types
+
+ # ...
+
+ agent = Agent(
+ model=Gemini(
+ retry_options=types.HttpRetryOptions(initial_delay=1, attempts=2),
+ )
+ )
+ ```
+ """
+
  @staticmethod
  @override
  def supported_models() -> list[str]:
@@ -191,7 +209,10 @@ def api_client(self) -> Client:
  The api client.
  """
  return Client(
- http_options=types.HttpOptions(headers=self._tracking_headers)
+ http_options=types.HttpOptions(
+ headers=self._tracking_headers,
+ retry_options=self.retry_options,
+ )
  )
 
  @cached_property