Allow explicit resolution order for @experiment

[bruno-f-cruz]

Adds two small, backward-compatible ways to control experiment selection when a script defines more than one @experiment: an order field (@experiment(name=..., order=-1), default 0) that lets you hint which experiment sorts to the top of the picker instead of relying on physical position in the file — sorting is ascending, so lower values appear earlier (e.g. order=-1 puts an experiment above the default order=0 ones, at the top of the list) — with ties falling back to declaration order via a stable sort in collect_clabe_experiments; and a new --experiment-name CLI flag that resolves an experiment by name and skips the interactive prompt entirely, unblocking non-interactive/scripted runs (raising SystemExit with the list of available names if the given name doesn't match). Both changes are additive with safe defaults (order=0, experiment_name=None) that preserve today's behavior exactly, touch only _experiments.py and cli.py, and are covered by new tests for name-based selection, the not-found error path, and order-with-ties stability.