BWI-73 live verify: headered bwi close notice must not overwrite client_version

Verification row for BWI-73: exercises bwi's only hub POST path (http_notify_close -> wi_hub_post /send) now that it declares x-llmmsg-client: bwi/1.1.3. Closing this row IS the test - the close notice is the headered /send. Pass condition: my roster client_version stays llmmsg-srv-mcp/2.61.19 and caller_kind does not become non_shim_declared.