A cd anywhere in a step is a no-op when the shell is already inside that folder

The Dagster rerun failed at step 2 because a recovery patch put cd dagster-quickstart in the middle of the command, after the shell was already inside it. The leading-cd guard did not cover that. The container prefix now wraps cd: a single relative folder that does not exist but names the current folder returns success. Any other cd, including a truly missing folder, behaves as before.