Use only Chat On Steroids Core for this authorized file test.

In TEST_PROJECT, check whether _cos_connection_test.txt exists.
If it exists, stop without modifying it. Otherwise use apply_patch
to create it with exactly one line, followed by a newline:
CoS is connected.

Read the file back through Core. Do not change anything else,
execute commands, install packages, launch workers, commit,
push, or deploy.
