Build summary for `ko resolve`

We do builds with `ko resolve` to have images and also a deployment YAML. However, we were wondering whether there would be an easy way to get a list of all images (and their digest) that are created as part of the `resolve` run (without parsing the output). If not, would a command line flag, e.g. `--bom` (bill of materials, or similar) an option? Thanks in advance for feedback.

Start at the `ko resolve` command and inspect how it currently reports images and produces deployment YAML. Define the expected machine-readable output for every generated image and digest, then determine whether it should be exposed through a new flag such as `--bom`; the work is done when users can obtain that complete list without parsing command output.

Written by the indexing model from the issue text.