chore(release): prepare crates for publishing

[zatevakhin]

summary

• prepare crates.io/docs.rs metadata, packaged documentation, and manual release-candidate guidance
• add exact local Rust 1.85.0 policy with deterministic package, license, and offline consumer checks
• preserve the ABI, backend boundary, native pin, and dual-license contract without publishing crates

validation

• formatting, clippy, model-free tests, docs.rs-style docs, sys/link checks, and exact MSRV validation pass
• extracted inventories, licenses, links, and offline downstream consumers pass
• sys-first workspace publish dry-run completes without uploading