Archive completed automation threads

[yvette-carlisle]

Summary

• call Codex app-server thread/archive after successful Decodex automation completion
• record best-effort archive events without failing completed runs when archive fails
• cover the archive protocol call with a fake app-server regression test

Verification

• cargo make fmt-rust
• cargo test -p decodex archive_thread_after_success_calls_app_server_archive_and_records_event -- --nocapture
• cargo make check-rust
• git diff --check