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>

pyproject.toml

@@ -211,9 +211,10 @@ aloha = ["lerobot[dataset]", "gym-aloha>=0.1.2,<0.2.0", "lerobot[scipy-dep]"]
 pusht = ["lerobot[dataset]", "gym-pusht>=0.1.5,<0.2.0", "pymunk>=6.6.0,<7.0.0"] # TODO: Fix pymunk version in gym-pusht instead
 libero = ["lerobot[dataset]", "lerobot[transformers-dep]", "hf-libero>=0.1.3,<0.2.0; sys_platform == 'linux'", "lerobot[scipy-dep]"]
 metaworld = ["lerobot[dataset]", "metaworld==3.0.0", "lerobot[scipy-dep]"]
-robomme = [
-    "robomme @ git+https://github.com/RoboMME/robomme_benchmark.git@main ; sys_platform == 'linux'",
-]
+# NOTE: robomme is NOT a pyproject extra — mani-skill hard-pins numpy<2
+# which conflicts with lerobot's numpy>=2 base pin, so the two trees can't
+# resolve into a single env. Install it only in the RoboMME Docker image
+# via `uv pip install --override` (see docker/Dockerfile.benchmark.robomme).
 
 # All
 all = [