test: have clean remove the non-PROGRAMS build products

test: have clean remove the non-PROGRAMS build products

clean removes everything derived from $(PROGRAMS), plus
test-bees-plan-lib.o by name.  It misses the rest of what the explicit
rules produce: the two generated .dep files, and the bench object and
binary.  A .dep left behind is the worse of the two, since it is
`-include`d on the next build and names header paths from the tree it
was generated in.

Name them all.

Assisted-by: Claude-Code:claude-opus-4-8
Assisted-by: Claude-Code:claude-opus-5