fix(robomme): make docs build + fast tests green

1. Docs: add robomme to _toctree.yml under Benchmarks so doc-builder's
   TOC integrity check stops rejecting the new page.

2. Fast tests: robomme's mani-skill transitively pins numpy<2 which is
   unsatisfiable against the project's numpy>=2 base pin, so `uv sync`
   couldn't resolve a universal lockfile.

   Drop robomme as a pyproject extra entirely — it truly cannot coexist
   with the rest of the dep tree. The Dockerfile installs robomme
   directly from its git URL via `uv pip install --override`, which was
   already the runtime path. pyproject, docs, env docstrings, and the
   CI job comment all now point to the docker-only install.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/benchmark_tests.yml

@@ -312,7 +312,8 @@ jobs:
           if-no-files-found: warn
 
   # ── ROBOMME ───────────────────────────────────────────────────────────────
-  # Isolated image: lerobot[robomme] only (mani-skill, SAPIEN, Vulkan chain)
+  # Isolated image: mani-skill/SAPIEN/Vulkan chain with gymnasium and numpy
+  # overrides (robomme can't be a pyproject extra due to numpy<2 pin).
   robomme-integration-test:
     name: RoboMME — build image + 1-episode eval
     runs-on: