/btw now defaults to --tools=read: the side turn gets only READ_ONLY
tools under a read-only context (fetch restricted to GET), with the main
session view so read-only reads (todo_list) see real state. --tools=full
keeps the previous whole-registry clone with a fresh session; --tools=no
turns tools off. When tools are off, the default read silently falls back
to no tools, while an explicit --tools read|full errors as before.