[codex] science-grade GRRT validation contracts

[Protonmatter]

Summary

This PR redirects the simulator toward a validated GRRT research-platform contract while preserving the existing Python reference and accelerator layering.

Changes include:

• adds explicit educational_proxy versus validated unpolarized transfer mode
• replaces coordinate-basis magnetic/pitch-angle shortcuts with Kerr metric and fluid-frame invariant helpers
• routes coefficient bricks and polarized transfer through the shared metric-aware plasma-frame helper
• updates WebGPU and static CUDA/Metal/HIP/OpenCL Stokes kernel assets to derive launch state/conserved momenta through ZAMO camera launch instead of fixed photon constants
• adds physics/kernel contract tests and validation docs/roadmap

Validation

• python -m pytest -q tests/test_synchrotron_polarized_transfer.py tests/test_radiative_transfer.py tests/test_native_kernel_assets.py tests/test_kerr.py
• python -m compileall blackhole_sim
• python -m pytest -q
• cargo fmt --check --manifest-path native/core/Cargo.toml
• cargo test --manifest-path native/core/Cargo.toml
• python -m blackhole_sim.accelerator_cli doctor --json --fail-on-emulation
• python -m blackhole_sim.benchmark_cli --json --nr 3 --ntheta 3 --nphi 4 --points 7 --iterations 1
• python -m blackhole_sim.accelerated_cli --width 32 --height 18 --max-steps 64 --output out\science_redirection_smoke.npz
• local Codex skill validation with quick_validate.py for all seven installed science skills

Not Claimed

• Direct browser WebGPU readback after the shader change was not rerun.
• Concrete Illinois v3 selected-dump checksum and ipole baseline are still pending.
• CUDA/Metal/HIP/OpenCL vendor SDK compilation was not run; those files remain static source assets.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep release artifacts behind manual dispatch

GitHub documents the push.tags filter as running the workflow when matching tags are pushed, so this new v* trigger turns every version-tag push into an artifact-delivery run that builds and uploads Python/native wheels even when no release was explicitly requested. The repository policy says .github/workflows/ is CI-only and must not publish releases without an explicit request, so this should be limited to workflow_dispatch until release work is intentionally requested.

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[chatgpt-codex-connector]

Catch singular metric divisions in field fallback

For snapshots whose radial grid includes the horizon (r = r_+) or samples that land exactly there, kerr_metric_covariant divides by Delta = 0 before this helper can fall back to the Euclidean norm, and ZeroDivisionError is not caught by the new exception list. That makes coefficient-brick precompute and polarized transfer abort on a single horizon cell even though this path is meant to have a compatibility fallback; guard the horizon or include this exception before using the metric result.

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