Task-006: Publish multi-platform CLI releases

[rsasaki0109]

Linked task

Task-006

Summary

• Build native MusubiCAD CLI archives for Linux x86-64, Windows x86-64, macOS Apple Silicon, and macOS Intel.
• Smoke-test every release binary through version reporting, OCCT regeneration, and semantic geometry diff; Linux also generates a complete DesignPatch review on Mesa Vulkan.
• Package the license, README, release quick start, bracket Design Graph, and review patch with every binary.
• Publish all archives plus SHA256SUMS only from a version tag whose commit is on main.
• Add README download and release-safety guidance.

Implementation notes

Pull requests run the full four-platform build matrix with read-only permissions. Only the tag-only publish job receives contents: write, and it runs after every native build passes. Tags must exactly match the opencad-cli Cargo version. Archives retain the historical opencad executable name for compatibility.

Tests added

• Four-platform release build matrix
• Exact CLI version contract
• Native OCCT bracket regeneration
• Cross-platform semantic 80 mm → 100 mm and regenerated mass evidence
• Linux Mesa Vulkan Design Review with two expected effects
• Archive layout contract for executable, license, docs, model, and patch
• Invalid package version/platform rejection

Validation

• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test --workspace
• Windows optimized release build
• Windows release binary regeneration and DX12 review smoke test
• Windows ZIP contract and SHA-256 generation
• Four-platform GitHub Release matrix, native smoke tests, archive contracts, and artifact uploads
• GitHub GFM README rendering and 21 relative link targets

Docs updated

• README download section and release badge
• docs/release-quickstart.md
• docs/developer-guide/releases.md
• Developer guide index

Known limitations

Archives are not code-signed or notarized. GitHub's headless macOS runners expose no Metal adapter, so macOS rendering is documented but cannot be exercised there. Desktop installers, signing, and CLI renaming are outside this one-task PR.