fix(cli): validate agent folder names for agent_engine

src/google/adk/cli/cli_deploy.py

@@ -764,6 +764,17 @@ def to_agent_engine(
   app_name = os.path.basename(agent_folder)
   display_name = display_name or app_name
   parent_folder = os.path.dirname(agent_folder)
+
+  # Validate folder name is a valid Python identifier for module imports
+  if not app_name.isidentifier():
+    click.secho(
+        f'Error: Agent folder name "{app_name}" must be a valid identifier '
+        'consisting of letters, digits, and underscores.',
+        fg='red',
+        err=True,
+    )
+    return
+
   adk_app_object = adk_app_object or 'root_agent'
   if adk_app_object not in ['root_agent', 'app']:
     click.echo(
@@ -789,7 +800,20 @@ def to_agent_engine(
     os.chdir(parent_folder)
     did_change_cwd = True
   tmp_app_name = app_name + '_tmp' + datetime.now().strftime('%Y%m%d_%H%M%S')
-  temp_folder = temp_folder or tmp_app_name
+
+  # Validate temp_folder if provided by user
+  if temp_folder:
+    if not temp_folder.isidentifier():
+      click.secho(
+          f'Error: The folder name "{temp_folder}" must be a valid identifier '
+          'consisting of letters, digits, and underscores.',
+          fg='red',
+          err=True,
+      )
+      return
+  else:
+    temp_folder = tmp_app_name
+
   agent_src_path = os.path.join(parent_folder, temp_folder)
   click.echo(f'Staging all files in: {agent_src_path}')
   # remove agent_src_path if it exists