[ooctipus]

Replace local learned-dynamics implementations with these PhysicsNeMo Robotics components:

• JointStateCodec + GravityEncoder: replace Isaac Lab's heading conversion and gravity-feature math.
• FieldNormalizer: replaces separate offline NeRD training/deployment normalization.
• RunningNormalizer: replaces SuperMimic's local RunningNorm in its world model, policy and critic.
• LearnedDynamicsSolver + DynamicsInferenceSession: replace local history/reset buffers, prediction orchestration and state-writeback/FK code; add resident temporal caching.

NeRD networks and contact encoders were already reused before this PR. Isaac Lab retains tasks, capture, physical-model checks, dataset loading, replay, optimization and checkpoint orchestration.

Actual code reduction: 59 production Python lines. 13 existing files change; including tests/docs, the net change is +20 lines. The main diff includes unmerged prerequisites.

Prototype inference: 4.0× faster at 128 worlds (1.30 → 0.324 ms); 12.2× at 4,096 (19.52 → 1.60 ms). RTX 5090, FP32, CUDA graphs; excludes collision, FK, sensors and policy/training. End-to-end throughput remains unmeasured.

Validated: 15 integration tests, MLP/NeRD training smokes, normalization parity, formatting and docs passed.

Migration: NeRD v2 checkpoints need refitting; SuperMimic checkpoints remain compatible. Both SuperMimic learners require PhysicsNeMo here.

Isaac Lab dependencies: #8825/#8826 and shared #8822. They do not require this follow-up's new support commit.

External dependency: PhysicsNeMo Robotics (internal repository, package physicsnemo_robotics), local branch feat/resident-dynamics-ownership, required commit e597e95bedb1f3f90637f178c045bc70c944e5d2. This support is unpublished; no dependency MR exists yet because push access was denied. This PR remains draft until publication and package compatibility are resolved.

Contribution checklist

• Read contribution guidelines and applied test-audit criteria
• Updated owner tests, documentation, migration notes and changelog fragments
• Audited dependency directions and avoided new integration modules
• Ran repository formatting/changelog checks
• Combined-branch validation complete
• Publish compatible PhysicsNeMo support and resolve installation pins
• Merge prerequisite task/recorder PRs