Add multi-circle tensor compute with smooth profiles

[chaibhave]

Summary

• add a MultiCircleTensorCompute that builds scalar fields for multiple circles/spheres with cosine, tanh, or sharp transitions
• validate circle inputs, broadcast inside/outside values, and support an optional background fallback while keeping the evaluation vectorized

Testing

• make -j2 (fails: missing /workspace/moose/framework/app.mk because the MOOSE submodule is unavailable in the environment)

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https://chatgpt.com/codex/tasks/task_e_68cb85e240f08321b7ab4977553630b5