feat: add Newton CUDA graph owner knob

[TATP-233]

Summary

• Add the explicit EnvCfg.newton_use_cuda_graph owner knob with bool validation and factory forwarding.
• Enable Newton CUDA graph replay by default for the Newton backend and all current Newton task owners; eager fallback remains owned by UniSim for ineligible drivers or capture failures.
• Require unisim-core>=1.6.0 in the standard and ROCm dependency profiles and update both lockfiles.
• Update bilingual backend docs, routing/config coverage, and the IsaacGym fixed-variant drift fixture for the stricter 1.6.0 kinematics scan.

Consumes the published unisim-core 1.6.0 release (unilabsim/unisim#144, released through #147).

Validation

• uv run pytest -q tests/base/backend/test_newton_backend_options.py tests/base/test_isaacgym_fixed_variants.py tests/envs/locomotion/g1/test_g1_owner_contract.py tests/scripts/test_train_scripts.py::test_offpolicy_flashsac_g1_motion_tracking_task_composes - 7 passed, 33 deselected
• uv lock --check
• ROCm lock resolution/check using the mirrored pyproject.rocm.toml and uv.rocm.lock
• make check
• make test-all - 1491 passed, 27 skipped, 598 deselected; benchmark smoke 34/34 module mode and 35/35 script mode
• Sphinx HTML build with autodoc disabled
• Full-budget A/B evidence on RTX 4090 was recorded at feat: add Newton CUDA graph owner knob #1605 using unisim Work: 显式化 registry 默认 backend 语义，禁止依赖注册顺序 #144 head 3402c8f: +48.57% final SPS, -35.77% wall time, reward parity.

Drives #1604.

[TATP-233]

Full-budget FlashSAC Newton validation completed on the current owner-knob head (800a8f7c), using an editable install of unilabsim/unisim#144 at 3402c8f.

Environment: RTX 4090, Warp reports CUDA mempool enabled. The graph run emitted no fallback warning. Both runs used seed 1, 2048 environments, 25000 iterations, AMP, and the canonical g1_motion_tracking Newton owner. The graph run disabled playback so the comparison covers the training loop.

Metric	Eager baseline	CUDA graph	Delta
Final SPS	34,953.0	51,928.9	+48.57%
Training wall time	1,553.85 s	998.03 s	-35.77%
Final mean reward	26.4967	29.1227	+2.6259
Best mean reward	34.1479	34.2186	+0.0706
Completed iterations	25,000 / 25,000	25,000 / 25,000	status completed

Command:

uv run --no-sync train --algo flashsac --task g1_motion_tracking --sim newton \
  env.newton_use_cuda_graph=true training.no_play=true

Artifacts:

• Eager: logs/flash_sac/G1MotionTrackingSAC/2026-09-17_14-26-19_newton/run_summary.json
• Graph: logs/flash_sac/G1MotionTrackingSAC/2026-09-17_17-58-25_newton/run_summary.json

The graph snapshot records env.newton_use_cuda_graph: true, 51,400,704 total env steps, final reward 29.1227, and best reward 34.2186.