Remove Evergreen workflow

[mrjf]

Summary

• remove the Evergreen agentic workflow source and compiled lock workflow
• remove the deterministic Evergreen trigger workflow
• remove Evergreen-only shared policy docs and vendored workflow skills

Verification

• gh aw compile
• apm compile (attempted; failed because this repository has no apm.yml)
• rg -n "evergreen|Evergreen" . --hidden --glob '!.git' --glob '!node_modules' --glob '!README.md' --glob '!.autoloop/programs/**' (no matches)
• git diff --cached --check