just: Add 'test' recipe covering the full hardware-free suite
There's a discoverable gap between 'just ci-fast' (what's actually gated)
and 'every check a contributor should run before pushing'. Folding ci-fast
and ci-slow into a single 'just test' makes the pre-push expectation
explicit without forcing contributors to remember both names.
Hardware tests stay separate ('just test-hardware') so the recipe runs
identically whether or not the developer has a camera or other dev hardware
attached.