Make ago adoption zero-config and expose policy provenance

[jackspirou]

Summary

• lead with the shared Go dialect and productive-boring motivation
• reduce native adoption to go get -tool and go tool ago
• make init optional, minimal, and aware of module and workspace roots
• report policy provenance through text and versioned JSON
• add a versioned config schema and command-level regression tests
• lead release notes with the native Go tool path and filter internal commits

Verification

• make check
• make prose
• make release-check
• make snapshot
• clean Sol autoreview at the pre-PR gate