Replaces the four not_implemented() stubs. mcp_status/set_mcp_enabled
reach the process-wide RmcpServer singleton (behind `#[cfg(feature =
"mcp")]`, with a not_implemented fallback for builds without it);
set_mcp_scope/mcp_access_log are plain settings/Store I/O and work in
every build regardless of the `mcp` cargo feature. The token is only
ever returned once, right when set_mcp_enabled mints it -- it is never
re-readable afterwards, same as any other freshly-issued secret.
iamdoubz
0ecc72f18f