[Tracking] Restore Newton VBD color balancing after Warp hang is fixed

Describe the bug

PR #7826 temporarily disables Warp's optional graph-color balancing pass when the Newton VBD manager colors its builder:

builder.color(balance_colors=False)

The initial graph coloring remains valid and is sufficient for VBD correctness, but skipping balancing may leave less-even color groups and should not become the permanent behavior.

The upstream defect is tracked in NVIDIA/warp#1964. Warp's balancer can alternate indefinitely between valid equal-ratio colorings; this was not covered by the earlier partial fix in NVIDIA/warp#816.

Keep this issue open after PR #7826 merges. Once an upstream fix is released and Isaac Lab consumes that Warp version, PR #7826's workaround should be superseded and balanced coloring restored.

Steps to reproduce

The full reproducer and analysis are in NVIDIA/warp#1964.

In Isaac Lab CI, the symptom is a worker timing out after 1000 seconds during simulation reset:

warp/_src/coloring.py:156 in graph_coloring_balance
newton/_src/sim/graph_coloring.py:294 in color_graph
newton/_src/sim/builder.py in color
isaaclab_newton/physics/vbd_manager.py in instantiate_builder_from_stage
isaaclab/sim/simulation_context.py in reset

The blamed deformable test varies by run because the shared VBD builder initialization hangs, rather than an individual test failing.

System Info

• Isaac Lab branch: develop at e86463df8
• Warp: 1.17.0
• Python: 3.12
• OS: Linux x86_64
• CI GPU: NVIDIA L40S

Additional context

Observed in three recent blocking isaaclab_contrib CI jobs:

• run 33963394703, job 101299175644
• run 34153472219, job 101840450098
• run 34155394372, job 101846147021

The temporary workaround in PR #7826 passed the focused Newton VBD tests and six consecutive runs of test_deformable_object.py without a hang.

Checklist

• I have checked that there is no similar open issue in the repo
• I have checked that the issue is related to Isaac Lab's Newton integration rather than Isaac Sim itself

Acceptance Criteria

• NVIDIA/warp#1964 is fixed with a regression test and the fix is included in a Warp release consumed by Isaac Lab.
• Remove or supersede PR #7826's balance_colors=False workaround and restore balanced coloring for both Newton VBD builder paths.
• Update the focused tests to verify the restored behavior.
• Run the complete deformable-object suite repeatedly without a graph-coloring timeout.