PimSim: executable worlds and physical-agent CI

Build the standard simulation and evaluation platform beneath ordinary DimOS applications.

Two product loops

1. World construction: authored, procedural, or captured sources compile into validated executable scene packages.
2. Physical CI: unchanged DimOS agents and skills run in those worlds and are verified, compared, and promoted to hardware.

Hyper-realistic means

Gaussian splats provide camera appearance. Clean cooked meshes provide collision, navigation, raycasting, contact, and MuJoCo physics. Semantics, devices, calibration, and alignment stay explicit.

Roadmap

1. Executable scene compiler
2. Unreal-to-splat and cooked-physics pipeline
3. Procedural scene families
4. Task, skill, trace, and promotion contracts
5. xArm physical pick/place gate
6. Flagship long-horizon mobile-manipulation mission
7. Real deployment-site capture and sim-real regression loop

Broad robot coverage, product UX, and training scale follow these gates.

Synced from DIM-1188 by mustafa

No files, tests, or entry points are named. Start by reviewing the linked DIM-1188 issue and the repository's existing simulation and CI structure, then narrow the roadmap to one explicitly scoped gate. Done should be defined by an implemented gate with a verifiable simulation or physical-agent evaluation.