docs: update autoloop go migration progress to iteration 137

- Update latest status to iteration 137 (2026-05-19 03:14 UTC)
- Best metric: 1067.50% (up from 75.06%)
- Corrected original_python_lines to 87,626
- Update PR reference to #56 (active) and note #17 (initial merge)
- Expand migration progress table through iteration 137
- Replace 141-module table with full 225 unique Go packages from
  migration-status.json on refs/pull/56/head
- Add note explaining metric >100% (test-migration entries + aliases)
- Update Go build/test validation through iteration 137
- Update next-up section from memory/autoloop Current Priorities
- Benchmark script run attempted; sandbox permission denied noted

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]