Builds the server identity map (serverInfo) both eras emit — the legacy lane in the initialize result, the modern lane in every result's _meta (Wymcp.Modern). name and version come from application config (:wymcp, :name / :version); the optional identity fields come from the :server_info router option (Wymcp.Router documents the accepted keys). Icon maps are whitelisted key-by-key — an unknown key is dropped with a logged warning naming it, so a misspelled key is findable instead of silently absent from the wire.