fix: Include the venv checksum file in the sources fields for all public linting tasks.

[Bill-hbrhbr]

Description

As discussed offline, a task containing both the sources and deps fields will always execute the tasks listed in deps, but it may skip running itself if the sources remain unchanged.

To ensure the parent task re-runs whenever the venv task is re-executed, we need to enforce this dependency by introducing the venv task checksum in sources. Otherwise, we risk missing tool version upgrades or inadvertently introducing linting issues.

Validation performed

• With the checksum files in sources, a re-run/ rebuild of venv properly triggers re-runs of all linting tasks.