Add prebuilt binary distribution plan for ncp-mcp-server

[madeinplutofabio]

Summary

cargo install ncp-mcp-server --locked is fine for Rust users, but many MCP adopters are not Rust users. The runtime ships per-OS archives via GitHub Releases (per Phase 3A.1); the adapter currently does not. This is real adoption friction.

Acceptance criteria

• Decide whether adapter binaries should ship via GitHub Releases. Document the decision either way.
• If yes: define the workflow shape (separate from existing release.yml which is runtime-only).
• Define a tag and workflow pattern that does NOT collide with runtime v* tags. The adapter tag pattern ncp-mcp-server-v* is already locked in docs/PUBLISHING.md "Adapter publish"; the new workflow must also trigger on that pattern only.
• Produce per-OS archives only for ncp-mcp-server (Linux x86_64, macOS arm64, Windows x86_64 minimum).
• Include SHA256 checksums.
• If accepted, update docs/PUBLISHING.md "Adapter publish" section accordingly.

Why this matters

Adoption friction is currently "install Rust 1.94 first, then cargo install". For an MCP server expected to ship into a host's config, that is a hard ask for non-Rust adopters.

Where to read

• docs/PUBLISHING.md §1 through §8 for the existing runtime release flow (template to mirror)
• docs/PUBLISHING.md "Adapter publish" section for the current adapter-publish flow (crates.io-only)
• .github/workflows/release.yml for the existing runtime release workflow