`uv sync` should handle a missing `uv lock`.

[konstin]

When trying to sync an empty workspace i got:

$ uv sync
warning: `uv sync` is experimental and may change without warning.
error: failed to read from file `/home/konsti/projects/workspace-git-path-dep-test/uv.lock`
  Caused by: No such file or directory (os error 2)

This error message should hint towards running uv lock.