dist: cross-language artifact and platform support matrix

[Fieldnote-Echo]

Summary

Define a cross-language artifact and platform support matrix for ordvec distributions.

This is an ecosystem compatibility issue. As ordvec grows beyond the Rust crate and Python wheel, downstream hosts need to know which artifacts exist, which platforms are supported, and how native libraries are named, linked, and versioned.

Current gap

crates.io and PyPI paths exist, and C/Go sidecars are repo-local. Future Node/WASM or JVM packages would add more surfaces. Without a checked matrix, packaging expectations can drift.

Proposed scope

Add a support matrix covering:

• Rust crate
• Python wheels/source builds
• repo-local C ABI
• Go wrapper
• future Node/WASM package
• future JVM package
• x86_64/aarch64 platform support
• Linux glibc/musl, macOS, Windows where applicable
• wasm support where applicable
• CPU baseline and SIMD expectations
• native library naming/loading strategy
• SBOM/provenance expectations
• version alignment across artifacts

Acceptance criteria

• Checked-in matrix documents supported and unsupported combinations clearly.
• CI has packaging smoke tests for each committed distribution path where practical.
• Release checklist references the matrix.
• Matrix aligns with release: pre-1.0 compatibility and SemVer policy #131 compatibility policy and policy: MSRV and feature stability matrix #132 MSRV/features policy.
• Docs make clear this is packaging compatibility, not a database service support matrix.

Non-goals

• No commitment to every platform by default.
• No managed package hosting beyond chosen registries.
• No downstream product adapter.