air: improve ergonomics for binding the Air to the transcript

In the current recursive verifier implementation, we use a fixed constant to initialize the capacity portion of the transcript. This can be a footgun since there is no mechanism to automatically update it if the Air changes.

There are a couple of ways in varying levels of complexity to make this easier.

- Use `insta` to validate that the ACE circuit digest matches the digest we use to initialize the transcript for the ProcessorAir
- Add a method on the Air which returns the ACE digest
- Investigate a method to use the same AirBuilder patterns to define the verifier's VLPI and bus boundary checks, and maybe even the quotient check, in a way that allows us to generate the ACE circuit from any Air without having to manually implement these checks in both the Air (for the native verifier) and the ACE (recursive verifier). This is more involved, but would make this critical path easier to audit and maintain.