docs: wire mjlab/maniskill/robotwin integration pages into toctree + fix xref

- Register the three integration pages in the Dataset & Benchmark toctree
  (were orphaned -> "document isn't included in any toctree" warnings).
- maniskill.md: replace fragile heading-anchor link with an explicit MyST
  label (maniskill-gap-analysis) so the gap-analysis cross-reference resolves.
- dataset_benchmark/index.md: drop trailing horizontal rule that ended the
  page on a transition (docutils ERROR in the wiki build).

Sphinx build exits 0 with the three payload docs warning-clean.

Author: geng-haoran

docs/source/dataset_benchmark/index.md

@@ -65,5 +65,3 @@ The RoboVerse Benchmark provides standardized evaluation protocols for:
 
 See [Benchmark Overview](benchmark/overview.md) for detailed evaluation protocols.
 
----
-

docs/source/dataset_benchmark/integrations/maniskill.md

@@ -22,7 +22,7 @@ Live report (with embedded videos and gap analysis):
   `T=20`, `final_cube_z=0.0198 m` under zero-delta target). It is a
   RoboVerse-flavored task, not a 1:1 reimplementation of PickCube-v1.
 - **Gap to numeric parity**: 10 items, all localised to one task
-  module. See the [gap analysis section](#what-it-takes-to-reach-1-1-parity)
+  module. See the [gap analysis section](maniskill-gap-analysis)
   below.
 
 ## Coverage
@@ -37,6 +37,7 @@ Live report (with embedded videos and gap analysis):
 All four roll out + render under the harness; zero-action reward sums
 range 2.3–5.4 (no task is succeeded by a stationary robot, as expected).
 
+(maniskill-gap-analysis)=
 ## What it takes to reach 1:1 parity
 
 `roboverse_pack/tasks/maniskill/pick_cube.py` needs:

docs/source/index.md

@@ -150,6 +150,9 @@ Scenes <dataset_benchmark/dataset/scenes>
 Benchmark Overview <dataset_benchmark/benchmark/overview>
 Benchmark Results <dataset_benchmark/benchmark/results>
 Benchmark Usage <dataset_benchmark/benchmark/usage>
+ManiSkill Integration <dataset_benchmark/integrations/maniskill>
+mjlab Integration <dataset_benchmark/integrations/mjlab>
+RoboTwin Integration <dataset_benchmark/integrations/robotwin>
 ```
 
 ```{toctree}