* fix(make): name what make clean deletes and refuse under a live gateway
`make help` described `make clean` as cleaning up "temporary files", but it
deletes backend/.deer-flow: the local database, users, threads, uploads,
memory, and secrets. Both Docker stacks mount that directory into the
deer-flow-gateway container, and `make stop` only stops local services, so
the data could be deleted under a running Gateway.
Say what is deleted in the help text and before deleting, and refuse while
the deer-flow-gateway container is running. The check runs before `make
stop`, which would otherwise stop the running stack's sandboxes first; a
missing or unreachable Docker passes.
* docs(changelog): reference #6351 for the make clean guard
* fix(make): share make clean's data list and pin stop before the delete
The help line listed "database, threads, uploads, secrets" while the
deletion notice also named users and memory. Define the list once in
RUNTIME_DATA_CONTENTS and use it in both.
Running sandbox containers left behind by `make down` are already stopped
by `make stop` (serve.sh --stop reaps deer-flow-sandbox*), which runs after
the guard and before the delete. Note that in the guard script, and pin
the ordering: the stub stop now records that the data still exists.
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>