Restore Result compatibility on safe VM leak-fix base

[proboscis]

Summary

Restore the VM leak-fix line on the last known safe base and add back the legacy doeff._vendor.Result shim required by current proboscis-ema imports.

This intentionally avoids the later deferred-segment cleanup commits that reintroduced the RuntimeError: internal error: no current segment failure under the TRD-023 pipeline shape.

Verification

• uv run pytest tests/test_vm_memory_leak.py -q in proboscis-ema with doeff rev d6ae0c81715a53c563cdf55087b139a9ad6c7987
  • 3 passed in 73.42s
• uv run --with mpmath python -m doeff run --program proboscis_ema.doeff.trading.entrypoints.trd023_report.p_trd023_report_5d_3model_pos5pct
  • no longer hits RuntimeError: internal error: no current segment
  • progresses into the real pipeline until an external NameResolutionError for influxdb.proboscis-ema.svc.cluster.local

Issue: vm-rust-memory-leak