"Silent" breaking and placing of blocks

At the moment, we rely on having to look at the target block to place it. We should offer a configurable alternative: silent place/break. Effectively this could still do hand animations as well as tell the server that we are facing the target, but looking at the block from a client-side perspective would not be a requirement.

No files or tests are named. Start by tracing the existing block-breaking and block-placement entry points and their target-facing checks, then determine where the configurable alternative belongs. Done means both actions support the described silent behavior while preserving the existing hand-animation and server-facing behavior.

Written by the indexing model from the issue text.