This PR adds a py.typed marker file to the google.adk package and updates the Flit configuration in pyproject.toml to include it in the distribution.

This allows static type checkers (like mypy or pyright) to recognize that the package supports type hints, in line with [PEP 561](https://www.python.org/dev/peps/pep-0561/).

This change is minimal, backward-compatible, and supports the goal of typed-first Python development.

Author: mohamadghaffari

pyproject.toml

@@ -145,6 +145,7 @@ exclude = ['src/**/*.sh']
 
 [tool.flit.module]
 name = "google.adk"
+include = ["py.typed"]
 
 [tool.isort]
 profile = "google"