Proposal: Allow for enforcning minimum bulk strategy on actions

# Is your feature request related to a problem?
Bulk actions silently fall back to slower strategies (:atomic_batches / :stream). When writing hot-path code we need to guarantee the fastest path and fail fast if it isn’t possible.

# Describe the solution you’d like
Allow an action-level option, e.g. bulk_min_strategy :atomic, that raises if the data layer can’t meet that minimum (:atomic, :atomic_batches, or :stream). Default = no minimum (current behaviour).

# Describe alternatives you’ve considered
Currently manually setting `bulk_options: [strategy: :atomic]`, which should trigger the same behaviour but is easy to forget

Start by tracing how action-level bulk_options selects among :atomic, :atomic_batches, and :stream, including where silent fallback occurs. Define how a bulk_min_strategy option would enforce the requested minimum and fail fast; done means the default remains unchanged and the requested minimum is honored.

Written by the indexing model from the issue text.