feat: Add ADK_DISABLE_LOAD_DOTENV environment variable that disables automatic loading of .env when running ADK cli, if set to true or 1

Fixes #3228

PiperOrigin-RevId: 825273905

src/google/adk/cli/cli.py

@@ -34,6 +34,7 @@ from ..sessions.base_session_service import BaseSessionService
 from ..sessions.in_memory_session_service import InMemorySessionService
 from ..sessions.session import Session
 from ..utils.context_utils import Aclosing
+from ..utils.env_utils import is_env_enabled
 from .utils import envs
 from .utils.agent_loader import AgentLoader
 
@@ -160,7 +161,8 @@ async def run_cli(
   root_agent = AgentLoader(agents_dir=agent_parent_dir).load_agent(
       agent_folder_name
   )
-  envs.load_dotenv_for_agent(agent_folder_name, agent_parent_dir)
+  if not is_env_enabled('ADK_DISABLE_LOAD_DOTENV'):
+    envs.load_dotenv_for_agent(agent_folder_name, agent_parent_dir)
   if input_file:
     session = await run_input_file(
         app_name=agent_folder_name,