fix pull script: everything in bash -c, run_shell_script doesn't use shell
prefect's run_shell_script executes each line as a subprocess binary call,
so shell builtins (cd, &&, etc) don't work at the top level. wrap all
commands in a single bash -c "..." invocation.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>