Keep Laya weights and workspace on CUDA

[linear3735]

Purpose

Upload Laya's 205 used tensors once and allocate 17 reusable workspace buffers. Validate shapes before allocation and release partial allocations on failure.

Part of #14. #21 is merged; this draft depends on #47.

The diff against main includes #47. Review this increment: 190 core/configuration lines for residency and workspace.

Tests now live under the repository-root tests/ directory. Cargo target names and test coverage are unchanged.

Test Plan

cargo fmt --all --check
cargo clippy --workspace --locked --all-targets -- -D warnings
cargo test --workspace --locked
cargo build --workspace --release --locked

On H800, compare uploaded tensors with the Torch conversion oracle and check workspace capacity and reuse. Prerequisites and exact opt-in commands are in the native residency/workspace recipe.

System1-Omni Version / Commit: 7574f19. Residency/workspace increment: 9ef493e → 2f5ff4b.

Test Result

Current CPU CI: 37 tests passed; 8 checkpoint/GPU tests skipped. fmt, strict Clippy and release build passed. This documentation-only follow-up also passed local strict MkDocs, shell syntax and rendered-anchor checks. The H800 results below are historical allocation/transfer checks; runtime source is unchanged and GPU tests were not rerun.

• All 205 uploaded tensor hashes matched the oracle.
• All 17 buffers passed two write/read rounds at three shapes, including 16×512.
• Weight allocations: 803.72 MiB. Largest workspace: 225.11 MiB. Both exclude CUDA and library overhead.

CI for 7574f19: Rust CI, Docs build, benchmark harness tests passed.

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