cmd_history was silently hiding the deleted flag, making it
impossible to tell from the output that a node had been deleted.
This masked the kernel-patterns deletion — looked like the node
existed in the log but wouldn't load.
Also adds merge-logs and diag-key diagnostic binaries, and makes
Node::to_capnp public for use by external tools.
Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>
