The query header now leads with the graph file it opened and its node count,
shown relative to the CWD when the graph sits underneath it and absolute when it
does not — surfacing the case where a query run from a parent project silently
answers from the wrong corpus. graph_path is optional, so the header is
byte-identical for callers that do not pass it; the CLI query command and the MCP
query tool, which already resolve the path for querylog, now pass it.
