Remove Evergreen workflows and install traces

[mrjf]

Summary

• remove the Evergreen source, lock, and trigger workflows
• remove the vendored Evergreen shared policy/template files
• remove the vendored Evergreen v1 shared skill pack
• remove the Autoloop handoff paragraph that referenced Evergreen
• delete the repo-level Evergreen labels because they were unused

Validation

• ran gh aw compile autoloop; it completed with the existing title-prefix deprecation warning
• ran apm compile; it reported this is not an APM project because no apm.yml exists
• ran git diff --check
• confirmed a repo-wide evergreen text search returns no matches
• confirmed no Evergreen-named labels, Actions secrets, or Actions variables remain