sphinx-fix

1Build: state=Finished  success=False  exit=1  build finished with problems, 1 warning.2 3Findings (1):4  Tier 2 — structural/parse (fix first; these mask warnings beneath them):5    [T2] toctree-nonexisting  doc/source/index.md:126          msg:    toctree contains reference to nonexisting document 'ray-contribute/old-name'7          fix:    Fix the toctree entry (entries are extensionless) to the current document name, or remove it.8          safety: mechanical9 10Unclassified (0) — no rule matched; resolve with the user, then file a skill-improvement ticket to add a rule:11 12Suppressed (0) — known-benign, not actionable:13 14Next: fix Tier 2 first (it masks others), then rebuild and re-run — do not assume one pass is complete.15