* refactor(model-cost): move the cost map inputs, fetch and register_model overlay into Rust
* fix(model-cost): keep main's compat helpers pure and move network tests to integration
ModelCostMapReloaded.model_cost_map now returns the alias-sharing table, so an alias registration after adopting a reload still reprices the owner. _finalize_model_cost_map reads a caller's map without size limits and installs nothing, through the new NativeModelCostMap.finalize. The unit tests that started a local server or a child interpreter now live in tests/integration/sdk/test_model_cost_fetch_sdk.py, and run_isolated gets direct tests for joining its blocking pool and leaving the fork gate alone.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>