Keep labels constraint; add --label dependencies to PR creation

Instead of removing the labels:[dependencies] safety constraint from the
codegen-agentic-fix safe-output, fix the root cause: the PR created by
update-copilot-dependency.yml was missing the label. Now the PR is
created with --label dependencies, matching the safe-output constraint.

Recompile codegen-agentic-fix.lock.yml.

Author: edburns