_recommend assumes sorted, deduped grids (core_grid[-1] = biggest, knee
sweeps run low->high). The CLI parsed --nodes/--cores in raw order, so
e.g. --cores 32,8,16 yielded nonsense. Sort+dedupe in cli.py and reject
non-positive/non-integer values; also normalize defensively inside
estimate() so the function is correct for any caller. Add estimate/cli
tests.