Spec create/update no longer hangs when contended, returns a retryable “locked” error

Creating or updating a spec from the MCP tools or the dashboard would hang indefinitely when another write was in progress, eventually timing out MCP clients and wedging the server. Spec writes now have a bounded lock wait, and if a write is currently in progress the MCP create/update tools and the dashboard’s new/edit/show pages surface a clear “being written, try again” message (with a retry flash on the dashboard) instead of hanging or crashing. Existing wedges are cleared on deploy of this version.