Separate tag namespace from the Go pipeline (v*.*.*) per the
blast-radius doctrine; artifacts publish to /host-agent/alpha/ and a
versioned dir, leaving /host-agent/latest/ on the Go build until
cutover. Linux = static musl, Windows = mingw (msvc/cargo-xwin stays
the local release path). Tag-vs-Cargo.toml version gate included.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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