feat(proxy): enable managed compression

[vishr]

Summary

• enable streaming-safe compression for Onebox-managed HTTPS routes
• keep dynamic proxy extensions composable beside managed defaults
• reserve managed filenames and middleware names against collisions
• update generated schema and proxy documentation

Verification

• just check
• go test -race ./internal/proxy
• Goal: just check, just web-check, local ob validate
• Monk: just server-check, just server-test, just feed-check, just web-check, local ob validate